journal.c source code [Linux/fs/jbd2/journal.c]

1	// SPDX-License-Identifier: GPL-2.0+
2	/*
3	* linux/fs/jbd2/journal.c
4	*
5	* Written by Stephen C. Tweedie <sct@redhat.com>, 1998
6	*
7	* Copyright 1998 Red Hat corp --- All Rights Reserved
8	*
9	* Generic filesystem journal-writing code; part of the ext2fs
10	* journaling system.
11	*
12	* This file manages journals: areas of disk reserved for logging
13	* transactional updates. This includes the kernel journaling thread
14	* which is responsible for scheduling updates to the log.
15	*
16	* We do not actually manage the physical storage of the journal in this
17	* file: that is left to a per-journal policy function, which allows us
18	* to store the journal within a filesystem-specified area for ext2
19	* journaling (ext2 can use a reserved inode for storing the log).
20	*/
21
22	#include <linux/module.h>
23	#include <linux/time.h>
24	#include <linux/fs.h>
25	#include <linux/jbd2.h>
26	#include <linux/errno.h>
27	#include <linux/slab.h>
28	#include <linux/init.h>
29	#include <linux/mm.h>
30	#include <linux/freezer.h>
31	#include <linux/pagemap.h>
32	#include <linux/kthread.h>
33	#include <linux/poison.h>
34	#include <linux/proc_fs.h>
35	#include <linux/seq_file.h>
36	#include <linux/math64.h>
37	#include <linux/hash.h>
38	#include <linux/log2.h>
39	#include <linux/vmalloc.h>
40	#include <linux/backing-dev.h>
41	#include <linux/bitops.h>
42	#include <linux/ratelimit.h>
43	#include <linux/sched/mm.h>
44
45	#define CREATE_TRACE_POINTS
46	#include <trace/events/jbd2.h>
47
48	#include <linux/uaccess.h>
49	#include <asm/page.h>
50
51	#ifdef CONFIG_JBD2_DEBUG
52	static ushort jbd2_journal_enable_debug __read_mostly;
53
54	module_param_named(jbd2_debug, jbd2_journal_enable_debug, ushort, `0644`);
55	MODULE_PARM_DESC(jbd2_debug, "Debugging level for jbd2");
56	#endif
57
58	EXPORT_SYMBOL(jbd2_journal_extend);
59	EXPORT_SYMBOL(jbd2_journal_stop);
60	EXPORT_SYMBOL(jbd2_journal_lock_updates);
61	EXPORT_SYMBOL(jbd2_journal_unlock_updates);
62	EXPORT_SYMBOL(jbd2_journal_get_write_access);
63	EXPORT_SYMBOL(jbd2_journal_get_create_access);
64	EXPORT_SYMBOL(jbd2_journal_get_undo_access);
65	EXPORT_SYMBOL(jbd2_journal_set_triggers);
66	EXPORT_SYMBOL(jbd2_journal_dirty_metadata);
67	EXPORT_SYMBOL(jbd2_journal_forget);
68	EXPORT_SYMBOL(jbd2_journal_flush);
69	EXPORT_SYMBOL(jbd2_journal_revoke);
70
71	EXPORT_SYMBOL(jbd2_journal_init_dev);
72	EXPORT_SYMBOL(jbd2_journal_init_inode);
73	EXPORT_SYMBOL(jbd2_journal_check_used_features);
74	EXPORT_SYMBOL(jbd2_journal_check_available_features);
75	EXPORT_SYMBOL(jbd2_journal_set_features);
76	EXPORT_SYMBOL(jbd2_journal_load);
77	EXPORT_SYMBOL(jbd2_journal_destroy);
78	EXPORT_SYMBOL(jbd2_journal_abort);
79	EXPORT_SYMBOL(jbd2_journal_errno);
80	EXPORT_SYMBOL(jbd2_journal_ack_err);
81	EXPORT_SYMBOL(jbd2_journal_clear_err);
82	EXPORT_SYMBOL(jbd2_log_wait_commit);
83	EXPORT_SYMBOL(jbd2_journal_start_commit);
84	EXPORT_SYMBOL(jbd2_journal_force_commit_nested);
85	EXPORT_SYMBOL(jbd2_journal_wipe);
86	EXPORT_SYMBOL(jbd2_journal_blocks_per_folio);
87	EXPORT_SYMBOL(jbd2_journal_invalidate_folio);
88	EXPORT_SYMBOL(jbd2_journal_try_to_free_buffers);
89	EXPORT_SYMBOL(jbd2_journal_force_commit);
90	EXPORT_SYMBOL(jbd2_journal_inode_ranged_write);
91	EXPORT_SYMBOL(jbd2_journal_inode_ranged_wait);
92	EXPORT_SYMBOL(jbd2_journal_finish_inode_data_buffers);
93	EXPORT_SYMBOL(jbd2_journal_init_jbd_inode);
94	EXPORT_SYMBOL(jbd2_journal_release_jbd_inode);
95	EXPORT_SYMBOL(jbd2_journal_begin_ordered_truncate);
96	EXPORT_SYMBOL(jbd2_inode_cache);
97
98	static int jbd2_journal_create_slab(size_t slab_size);
99
100	#ifdef CONFIG_JBD2_DEBUG
101	void __jbd2_debug(int level, const char file, const* char *func,
102	unsigned int line, const char *fmt, ...)
103	{
104	struct va_format vaf;
105	va_list args;
106
107	if (level > jbd2_journal_enable_debug)
108	return;
109	va_start(args, fmt);
110	vaf.fmt = fmt;
111	vaf.va = &args;
112	printk(KERN_DEBUG "%s: (%s, %u): %pV", file, func, line, &vaf);
113	va_end(args);
114	}
115	#endif
116
117	/ Checksumming functions /
118	static __be32 jbd2_superblock_csum(journal_superblock_t *sb)
119	{
120	__u32 csum;
121	__be32 old_csum;
122
123	old_csum = sb->s_checksum;
124	sb->s_checksum = `0`;
125	csum = jbd2_chksum(crc: ~`0`, address: (char )sb, length: sizeof*(journal_superblock_t));
126	sb->s_checksum = old_csum;
127
128	return cpu_to_be32(csum);
129	}
130
131	/*
132	* Helper function used to manage commit timeouts
133	*/
134
135	static void commit_timeout(struct timer_list *t)
136	{
137	journal_t *journal = timer_container_of(journal, t, j_commit_timer);
138
139	wake_up_process(tsk: journal->j_task);
140	}
141
142	/*
143	* kjournald2: The main thread function used to manage a logging device
144	* journal.
145	*
146	* This kernel thread is responsible for two things:
147	*
148	* 1) COMMIT: Every so often we need to commit the current state of the
149	* filesystem to disk. The journal thread is responsible for writing
150	* all of the metadata buffers to disk. If a fast commit is ongoing
151	* journal thread waits until it's done and then continues from
152	* there on.
153	*
154	* 2) CHECKPOINT: We cannot reuse a used section of the log file until all
155	* of the data in that part of the log has been rewritten elsewhere on
156	* the disk. Flushing these old buffers to reclaim space in the log is
157	* known as checkpointing, and this thread is responsible for that job.
158	*/
159
160	static int kjournald2(void *arg)
161	{
162	journal_t *journal = arg;
163	transaction_t *transaction;
164
165	/*
166	* Set up an interval timer which can be used to trigger a commit wakeup
167	* after the commit interval expires
168	*/
169	timer_setup(&journal->j_commit_timer, commit_timeout, `0`);
170
171	set_freezable();
172
173	/ Record that the journal thread is running /
174	journal->j_task = current;
175	wake_up(&journal->j_wait_done_commit);
176
177	/*
178	* Make sure that no allocations from this kernel thread will ever
179	* recurse to the fs layer because we are responsible for the
180	* transaction commit and any fs involvement might get stuck waiting for
181	* the trasn. commit.
182	*/
183	memalloc_nofs_save();
184
185	/*
186	* And now, wait forever for commit wakeup events.
187	*/
188	write_lock(&journal->j_state_lock);
189
190	loop:
191	if (journal->j_flags & JBD2_UNMOUNT)
192	goto end_loop;
193
194	jbd2_debug(`1`, "commit_sequence=%u, commit_request=%u\n",
195	journal->j_commit_sequence, journal->j_commit_request);
196
197	if (journal->j_commit_sequence != journal->j_commit_request) {
198	jbd2_debug(`1`, "OK, requests differ\n");
199	write_unlock(&journal->j_state_lock);
200	timer_delete_sync(timer: &journal->j_commit_timer);
201	jbd2_journal_commit_transaction(journal);
202	write_lock(&journal->j_state_lock);
203	goto loop;
204	}
205
206	wake_up(&journal->j_wait_done_commit);
207	if (freezing(current)) {
208	/*
209	* The simpler the better. Flushing journal isn't a
210	* good idea, because that depends on threads that may
211	* be already stopped.
212	*/
213	jbd2_debug(`1`, "Now suspending kjournald2\n");
214	write_unlock(&journal->j_state_lock);
215	try_to_freeze();
216	write_lock(&journal->j_state_lock);
217	} else {
218	/*
219	* We assume on resume that commits are already there,
220	* so we don't sleep
221	*/
222	DEFINE_WAIT(wait);
223
224	prepare_to_wait(wq_head: &journal->j_wait_commit, wq_entry: &wait,
225	TASK_INTERRUPTIBLE);
226	transaction = journal->j_running_transaction;
227	if (transaction == NULL \|\|
228	time_before(jiffies, transaction->t_expires)) {
229	write_unlock(&journal->j_state_lock);
230	schedule();
231	write_lock(&journal->j_state_lock);
232	}
233	finish_wait(wq_head: &journal->j_wait_commit, wq_entry: &wait);
234	}
235
236	jbd2_debug(`1`, "kjournald2 wakes\n");
237
238	/*
239	* Were we woken up by a commit wakeup event?
240	*/
241	transaction = journal->j_running_transaction;
242	if (transaction && time_after_eq(jiffies, transaction->t_expires)) {
243	journal->j_commit_request = transaction->t_tid;
244	jbd2_debug(`1`, "woke because of timeout\n");
245	}
246	goto loop;
247
248	end_loop:
249	timer_delete_sync(timer: &journal->j_commit_timer);
250	journal->j_task = NULL;
251	wake_up(&journal->j_wait_done_commit);
252	jbd2_debug(`1`, "Journal thread exiting.\n");
253	write_unlock(&journal->j_state_lock);
254	return `0`;
255	}
256
257	static int jbd2_journal_start_thread(journal_t *journal)
258	{
259	struct task_struct *t;
260
261	t = kthread_run(kjournald2, journal, "jbd2/%s",
262	journal->j_devname);
263	if (IS_ERR(ptr: t))
264	return PTR_ERR(ptr: t);
265
266	wait_event(journal->j_wait_done_commit, journal->j_task != NULL);
267	return `0`;
268	}
269
270	static void journal_kill_thread(journal_t *journal)
271	{
272	write_lock(&journal->j_state_lock);
273	journal->j_flags \|= JBD2_UNMOUNT;
274
275	while (journal->j_task) {
276	write_unlock(&journal->j_state_lock);
277	wake_up(&journal->j_wait_commit);
278	wait_event(journal->j_wait_done_commit, journal->j_task == NULL);
279	write_lock(&journal->j_state_lock);
280	}
281	write_unlock(&journal->j_state_lock);
282	}
283
284	static inline bool jbd2_data_needs_escaping(char *data)
285	{
286	return ((__be32 )data) == cpu_to_be32(JBD2_MAGIC_NUMBER);
287	}
288
289	static inline void jbd2_data_do_escape(char *data)
290	{
291	((unsigned* int *)data) = `0`;
292	}
293
294	/*
295	* jbd2_journal_write_metadata_buffer: write a metadata buffer to the journal.
296	*
297	* Writes a metadata buffer to a given disk block. The actual IO is not
298	* performed but a new buffer_head is constructed which labels the data
299	* to be written with the correct destination disk block.
300	*
301	* Any magic-number escaping which needs to be done will cause a
302	* copy-out here. If the buffer happens to start with the
303	* JBD2_MAGIC_NUMBER, then we can't write it to the log directly: the
304	* magic number is only written to the log for descripter blocks. In
305	* this case, we copy the data and replace the first word with 0, and we
306	* return a result code which indicates that this buffer needs to be
307	* marked as an escaped buffer in the corresponding log descriptor
308	* block. The missing word can then be restored when the block is read
309	* during recovery.
310	*
311	* If the source buffer has already been modified by a new transaction
312	* since we took the last commit snapshot, we use the frozen copy of
313	* that data for IO. If we end up using the existing buffer_head's data
314	* for the write, then we have to make sure nobody modifies it while the
315	* IO is in progress. do_get_write_access() handles this.
316	*
317	* The function returns a pointer to the buffer_head to be used for IO.
318	*
319	*
320	* Return value:
321	* =0: Finished OK without escape
322	* =1: Finished OK with escape
323	*/
324
325	int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
326	struct journal_head *jh_in,
327	struct buffer_head **bh_out,
328	sector_t blocknr)
329	{
330	int do_escape = `0`;
331	struct buffer_head *new_bh;
332	struct folio *new_folio;
333	unsigned int new_offset;
334	struct buffer_head *bh_in = jh2bh(jh: jh_in);
335	journal_t *journal = transaction->t_journal;
336
337	/*
338	* The buffer really shouldn't be locked: only the current committing
339	* transaction is allowed to write it, so nobody else is allowed
340	* to do any IO.
341	*
342	* akpm: except if we're journalling data, and write() output is
343	* also part of a shared mapping, and another thread has
344	* decided to launch a writepage() against this buffer.
345	*/
346	J_ASSERT_BH(bh_in, buffer_jbddirty(bh_in));
347
348	new_bh = alloc_buffer_head(GFP_NOFS\|__GFP_NOFAIL);
349
350	/ keep subsequent assertions sane /
351	atomic_set(v: &new_bh->b_count, i: `1`);
352
353	spin_lock(lock: &jh_in->b_state_lock);
354	/*
355	* If a new transaction has already done a buffer copy-out, then
356	* we use that version of the data for the commit.
357	*/
358	if (jh_in->b_frozen_data) {
359	new_folio = virt_to_folio(x: jh_in->b_frozen_data);
360	new_offset = offset_in_folio(new_folio, jh_in->b_frozen_data);
361	do_escape = jbd2_data_needs_escaping(data: jh_in->b_frozen_data);
362	if (do_escape)
363	jbd2_data_do_escape(data: jh_in->b_frozen_data);
364	} else {
365	char *tmp;
366	char *mapped_data;
367
368	new_folio = bh_in->b_folio;
369	new_offset = offset_in_folio(new_folio, bh_in->b_data);
370	mapped_data = kmap_local_folio(folio: new_folio, offset: new_offset);
371	/*
372	* Fire data frozen trigger if data already wasn't frozen. Do
373	* this before checking for escaping, as the trigger may modify
374	* the magic offset. If a copy-out happens afterwards, it will
375	* have the correct data in the buffer.
376	*/
377	jbd2_buffer_frozen_trigger(jh: jh_in, mapped_data,
378	triggers: jh_in->b_triggers);
379	do_escape = jbd2_data_needs_escaping(data: mapped_data);
380	kunmap_local(mapped_data);
381	/*
382	* Do we need to do a data copy?
383	*/
384	if (!do_escape)
385	goto escape_done;
386
387	spin_unlock(lock: &jh_in->b_state_lock);
388	tmp = jbd2_alloc(size: bh_in->b_size, GFP_NOFS \| __GFP_NOFAIL);
389	spin_lock(lock: &jh_in->b_state_lock);
390	if (jh_in->b_frozen_data) {
391	jbd2_free(ptr: tmp, size: bh_in->b_size);
392	goto copy_done;
393	}
394
395	jh_in->b_frozen_data = tmp;
396	memcpy_from_folio(to: tmp, folio: new_folio, offset: new_offset, len: bh_in->b_size);
397	/*
398	* This isn't strictly necessary, as we're using frozen
399	* data for the escaping, but it keeps consistency with
400	* b_frozen_data usage.
401	*/
402	jh_in->b_frozen_triggers = jh_in->b_triggers;
403
404	copy_done:
405	new_folio = virt_to_folio(x: jh_in->b_frozen_data);
406	new_offset = offset_in_folio(new_folio, jh_in->b_frozen_data);
407	jbd2_data_do_escape(data: jh_in->b_frozen_data);
408	}
409
410	escape_done:
411	folio_set_bh(bh: new_bh, folio: new_folio, offset: new_offset);
412	new_bh->b_size = bh_in->b_size;
413	new_bh->b_bdev = journal->j_dev;
414	new_bh->b_blocknr = blocknr;
415	new_bh->b_private = bh_in;
416	set_buffer_mapped(new_bh);
417	set_buffer_dirty(new_bh);
418
419	*bh_out = new_bh;
420
421	/*
422	* The to-be-written buffer needs to get moved to the io queue,
423	* and the original buffer whose contents we are shadowing or
424	* copying is moved to the transaction's shadow queue.
425	*/
426	JBUFFER_TRACE(jh_in, "file as BJ_Shadow");
427	spin_lock(lock: &journal->j_list_lock);
428	__jbd2_journal_file_buffer(jh_in, transaction, BJ_Shadow);
429	spin_unlock(lock: &journal->j_list_lock);
430	set_buffer_shadow(bh_in);
431	spin_unlock(lock: &jh_in->b_state_lock);
432
433	return do_escape;
434	}
435
436	/*
437	* Allocation code for the journal file. Manage the space left in the
438	* journal, so that we can begin checkpointing when appropriate.
439	*/
440
441	/*
442	* Called with j_state_lock locked for writing.
443	* Returns true if a transaction commit was started.
444	*/
445	static int __jbd2_log_start_commit(journal_t *journal, tid_t target)
446	{
447	/ Return if the txn has already requested to be committed /
448	if (journal->j_commit_request == target)
449	return `0`;
450
451	/*
452	* The only transaction we can possibly wait upon is the
453	* currently running transaction (if it exists). Otherwise,
454	* the target tid must be an old one.
455	*/
456	if (journal->j_running_transaction &&
457	journal->j_running_transaction->t_tid == target) {
458	/*
459	* We want a new commit: OK, mark the request and wakeup the
460	* commit thread. We do _not_ do the commit ourselves.
461	*/
462
463	journal->j_commit_request = target;
464	jbd2_debug(`1`, "JBD2: requesting commit %u/%u\n",
465	journal->j_commit_request,
466	journal->j_commit_sequence);
467	journal->j_running_transaction->t_requested = jiffies;
468	wake_up(&journal->j_wait_commit);
469	return `1`;
470	} else if (!tid_geq(x: journal->j_commit_request, y: target))
471	/ This should never happen, but if it does, preserve*
472	the evidence before kjournald goes into a loop and
473	increments j_commit_sequence beyond all recognition. /*
474	WARN_ONCE(`1`, "JBD2: bad log_start_commit: %u %u %u %u\n",
475	journal->j_commit_request,
476	journal->j_commit_sequence,
477	target, journal->j_running_transaction ?
478	journal->j_running_transaction->t_tid : `0`);
479	return `0`;
480	}
481
482	int jbd2_log_start_commit(journal_t *journal, tid_t tid)
483	{
484	int ret;
485
486	write_lock(&journal->j_state_lock);
487	ret = __jbd2_log_start_commit(journal, target: tid);
488	write_unlock(&journal->j_state_lock);
489	return ret;
490	}
491
492	/*
493	* Force and wait any uncommitted transactions. We can only force the running
494	* transaction if we don't have an active handle, otherwise, we will deadlock.
495	* Returns: <0 in case of error,
496	* 0 if nothing to commit,
497	* 1 if transaction was successfully committed.
498	*/
499	static int __jbd2_journal_force_commit(journal_t *journal)
500	{
501	transaction_t *transaction = NULL;
502	tid_t tid;
503	int need_to_start = `0`, ret = `0`;
504
505	read_lock(&journal->j_state_lock);
506	if (journal->j_running_transaction && !current->journal_info) {
507	transaction = journal->j_running_transaction;
508	if (!tid_geq(x: journal->j_commit_request, y: transaction->t_tid))
509	need_to_start = `1`;
510	} else if (journal->j_committing_transaction)
511	transaction = journal->j_committing_transaction;
512
513	if (!transaction) {
514	/ Nothing to commit /
515	read_unlock(&journal->j_state_lock);
516	return `0`;
517	}
518	tid = transaction->t_tid;
519	read_unlock(&journal->j_state_lock);
520	if (need_to_start)
521	jbd2_log_start_commit(journal, tid);
522	ret = jbd2_log_wait_commit(journal, tid);
523	if (!ret)
524	ret = `1`;
525
526	return ret;
527	}
528
529	/**
530	* jbd2_journal_force_commit_nested - Force and wait upon a commit if the
531	* calling process is not within transaction.
532	*
533	* @journal: journal to force
534	* Returns true if progress was made.
535	*
536	* This is used for forcing out undo-protected data which contains
537	* bitmaps, when the fs is running out of space.
538	*/
539	int jbd2_journal_force_commit_nested(journal_t *journal)
540	{
541	int ret;
542
543	ret = __jbd2_journal_force_commit(journal);
544	return ret > `0`;
545	}
546
547	/**
548	* jbd2_journal_force_commit() - force any uncommitted transactions
549	* @journal: journal to force
550	*
551	* Caller want unconditional commit. We can only force the running transaction
552	* if we don't have an active handle, otherwise, we will deadlock.
553	*/
554	int jbd2_journal_force_commit(journal_t *journal)
555	{
556	int ret;
557
558	J_ASSERT(!current->journal_info);
559	ret = __jbd2_journal_force_commit(journal);
560	if (ret > `0`)
561	ret = `0`;
562	return ret;
563	}
564
565	/*
566	* Start a commit of the current running transaction (if any). Returns true
567	* if a transaction is going to be committed (or is currently already
568	* committing), and fills its tid in at *ptid
569	*/
570	int jbd2_journal_start_commit(journal_t journal, tid_t ptid)
571	{
572	int ret = `0`;
573
574	write_lock(&journal->j_state_lock);
575	if (journal->j_running_transaction) {
576	tid_t tid = journal->j_running_transaction->t_tid;
577
578	__jbd2_log_start_commit(journal, target: tid);
579	/ There's a running transaction and we've just made sure*
580	* it's commit has been scheduled. */
581	if (ptid)
582	*ptid = tid;
583	ret = `1`;
584	} else if (journal->j_committing_transaction) {
585	/*
586	* If commit has been started, then we have to wait for
587	* completion of that transaction.
588	*/
589	if (ptid)
590	*ptid = journal->j_committing_transaction->t_tid;
591	ret = `1`;
592	}
593	write_unlock(&journal->j_state_lock);
594	return ret;
595	}
596
597	/*
598	* Return 1 if a given transaction has not yet sent barrier request
599	* connected with a transaction commit. If 0 is returned, transaction
600	* may or may not have sent the barrier. Used to avoid sending barrier
601	* twice in common cases.
602	*/
603	int jbd2_trans_will_send_data_barrier(journal_t *journal, tid_t tid)
604	{
605	int ret = `0`;
606	transaction_t commit_trans, running_trans;
607
608	if (!(journal->j_flags & JBD2_BARRIER))
609	return `0`;
610	read_lock(&journal->j_state_lock);
611	/ Transaction already committed? /
612	if (tid_geq(x: journal->j_commit_sequence, y: tid))
613	goto out;
614	commit_trans = journal->j_committing_transaction;
615	if (!commit_trans \|\| commit_trans->t_tid != tid) {
616	running_trans = journal->j_running_transaction;
617	/*
618	* The query transaction hasn't started committing,
619	* it must still be running.
620	*/
621	if (WARN_ON_ONCE(!running_trans \|\|
622	running_trans->t_tid != tid))
623	goto out;
624
625	running_trans->t_need_data_flush = `1`;
626	ret = `1`;
627	goto out;
628	}
629	/*
630	* Transaction is being committed and we already proceeded to
631	* submitting a flush to fs partition?
632	*/
633	if (journal->j_fs_dev != journal->j_dev) {
634	if (!commit_trans->t_need_data_flush \|\|
635	commit_trans->t_state >= T_COMMIT_DFLUSH)
636	goto out;
637	} else {
638	if (commit_trans->t_state >= T_COMMIT_JFLUSH)
639	goto out;
640	}
641	ret = `1`;
642	out:
643	read_unlock(&journal->j_state_lock);
644	return ret;
645	}
646	EXPORT_SYMBOL(jbd2_trans_will_send_data_barrier);
647
648	/*
649	* Wait for a specified commit to complete.
650	* The caller may not hold the journal lock.
651	*/
652	int jbd2_log_wait_commit(journal_t *journal, tid_t tid)
653	{
654	int err = `0`;
655
656	read_lock(&journal->j_state_lock);
657	#ifdef CONFIG_PROVE_LOCKING
658	/*
659	* Some callers make sure transaction is already committing and in that
660	* case we cannot block on open handles anymore. So don't warn in that
661	* case.
662	*/
663	if (tid_gt(tid, journal->j_commit_sequence) &&
664	(!journal->j_committing_transaction \|\|
665	journal->j_committing_transaction->t_tid != tid)) {
666	read_unlock(&journal->j_state_lock);
667	jbd2_might_wait_for_commit(journal);
668	read_lock(&journal->j_state_lock);
669	}
670	#endif
671	#ifdef CONFIG_JBD2_DEBUG
672	if (!tid_geq(journal->j_commit_request, tid)) {
673	printk(KERN_ERR
674	"%s: error: j_commit_request=%u, tid=%u\n",
675	__func__, journal->j_commit_request, tid);
676	}
677	#endif
678	while (tid_gt(x: tid, y: journal->j_commit_sequence)) {
679	jbd2_debug(`1`, "JBD2: want %u, j_commit_sequence=%u\n",
680	tid, journal->j_commit_sequence);
681	read_unlock(&journal->j_state_lock);
682	wake_up(&journal->j_wait_commit);
683	wait_event(journal->j_wait_done_commit,
684	!tid_gt(tid, journal->j_commit_sequence));
685	read_lock(&journal->j_state_lock);
686	}
687	read_unlock(&journal->j_state_lock);
688
689	if (unlikely(is_journal_aborted(journal)))
690	err = -EIO;
691	return err;
692	}
693
694	/*
695	* Start a fast commit. If there's an ongoing fast or full commit wait for
696	* it to complete. Returns 0 if a new fast commit was started. Returns -EALREADY
697	* if a fast commit is not needed, either because there's an already a commit
698	* going on or this tid has already been committed. Returns -EINVAL if no jbd2
699	* commit has yet been performed.
700	*/
701	int jbd2_fc_begin_commit(journal_t *journal, tid_t tid)
702	{
703	if (unlikely(is_journal_aborted(journal)))
704	return -EIO;
705	/*
706	* Fast commits only allowed if at least one full commit has
707	* been processed.
708	*/
709	if (!journal->j_stats.ts_tid)
710	return -EINVAL;
711
712	write_lock(&journal->j_state_lock);
713	if (tid_geq(x: journal->j_commit_sequence, y: tid)) {
714	write_unlock(&journal->j_state_lock);
715	return -EALREADY;
716	}
717
718	if (journal->j_flags & JBD2_FULL_COMMIT_ONGOING \|\|
719	(journal->j_flags & JBD2_FAST_COMMIT_ONGOING)) {
720	DEFINE_WAIT(wait);
721
722	prepare_to_wait(wq_head: &journal->j_fc_wait, wq_entry: &wait,
723	TASK_UNINTERRUPTIBLE);
724	write_unlock(&journal->j_state_lock);
725	schedule();
726	finish_wait(wq_head: &journal->j_fc_wait, wq_entry: &wait);
727	return -EALREADY;
728	}
729	journal->j_flags \|= JBD2_FAST_COMMIT_ONGOING;
730	write_unlock(&journal->j_state_lock);
731
732	return `0`;
733	}
734	EXPORT_SYMBOL(jbd2_fc_begin_commit);
735
736	/*
737	* Stop a fast commit. If fallback is set, this function starts commit of
738	* TID tid before any other fast commit can start.
739	*/
740	static int __jbd2_fc_end_commit(journal_t *journal, tid_t tid, bool fallback)
741	{
742	if (journal->j_fc_cleanup_callback)
743	journal->j_fc_cleanup_callback(journal, `0`, tid);
744	write_lock(&journal->j_state_lock);
745	journal->j_flags &= ~JBD2_FAST_COMMIT_ONGOING;
746	if (fallback)
747	journal->j_flags \|= JBD2_FULL_COMMIT_ONGOING;
748	write_unlock(&journal->j_state_lock);
749	wake_up(&journal->j_fc_wait);
750	if (fallback)
751	return jbd2_complete_transaction(journal, tid);
752	return `0`;
753	}
754
755	int jbd2_fc_end_commit(journal_t *journal)
756	{
757	return __jbd2_fc_end_commit(journal, tid: `0`, fallback: false);
758	}
759	EXPORT_SYMBOL(jbd2_fc_end_commit);
760
761	int jbd2_fc_end_commit_fallback(journal_t *journal)
762	{
763	tid_t tid;
764
765	read_lock(&journal->j_state_lock);
766	tid = journal->j_running_transaction ?
767	journal->j_running_transaction->t_tid : `0`;
768	read_unlock(&journal->j_state_lock);
769	return __jbd2_fc_end_commit(journal, tid, fallback: true);
770	}
771	EXPORT_SYMBOL(jbd2_fc_end_commit_fallback);
772
773	/ Return 1 when transaction with given tid has already committed. /
774	int jbd2_transaction_committed(journal_t *journal, tid_t tid)
775	{
776	return tid_geq(READ_ONCE(journal->j_commit_sequence), y: tid);
777	}
778	EXPORT_SYMBOL(jbd2_transaction_committed);
779
780	/*
781	* When this function returns the transaction corresponding to tid
782	* will be completed. If the transaction has currently running, start
783	* committing that transaction before waiting for it to complete. If
784	* the transaction id is stale, it is by definition already completed,
785	* so just return SUCCESS.
786	*/
787	int jbd2_complete_transaction(journal_t *journal, tid_t tid)
788	{
789	int need_to_wait = `1`;
790
791	read_lock(&journal->j_state_lock);
792	if (journal->j_running_transaction &&
793	journal->j_running_transaction->t_tid == tid) {
794	if (journal->j_commit_request != tid) {
795	/ transaction not yet started, so request it /
796	read_unlock(&journal->j_state_lock);
797	jbd2_log_start_commit(journal, tid);
798	goto wait_commit;
799	}
800	} else if (!(journal->j_committing_transaction &&
801	journal->j_committing_transaction->t_tid == tid))
802	need_to_wait = `0`;
803	read_unlock(&journal->j_state_lock);
804	if (!need_to_wait)
805	return `0`;
806	wait_commit:
807	return jbd2_log_wait_commit(journal, tid);
808	}
809	EXPORT_SYMBOL(jbd2_complete_transaction);
810
811	/*
812	* Log buffer allocation routines:
813	*/
814
815	int jbd2_journal_next_log_block(journal_t journal, unsigned* long long *retp)
816	{
817	unsigned long blocknr;
818
819	write_lock(&journal->j_state_lock);
820	J_ASSERT(journal->j_free > `1`);
821
822	blocknr = journal->j_head;
823	journal->j_head++;
824	journal->j_free--;
825	if (journal->j_head == journal->j_last)
826	journal->j_head = journal->j_first;
827	write_unlock(&journal->j_state_lock);
828	return jbd2_journal_bmap(journal, blocknr, retp);
829	}
830
831	/ Map one fast commit buffer for use by the file system /
832	int jbd2_fc_get_buf(journal_t journal, struct* buffer_head **bh_out)
833	{
834	unsigned long long pblock;
835	unsigned long blocknr;
836	int ret = `0`;
837	struct buffer_head *bh;
838	int fc_off;
839
840	*bh_out = NULL;
841
842	if (journal->j_fc_off + journal->j_fc_first >= journal->j_fc_last)
843	return -EINVAL;
844
845	fc_off = journal->j_fc_off;
846	blocknr = journal->j_fc_first + fc_off;
847	journal->j_fc_off++;
848	ret = jbd2_journal_bmap(journal, blocknr, &pblock);
849	if (ret)
850	return ret;
851
852	bh = __getblk(bdev: journal->j_dev, block: pblock, size: journal->j_blocksize);
853	if (!bh)
854	return -ENOMEM;
855
856	journal->j_fc_wbuf[fc_off] = bh;
857
858	*bh_out = bh;
859
860	return `0`;
861	}
862	EXPORT_SYMBOL(jbd2_fc_get_buf);
863
864	/*
865	* Wait on fast commit buffers that were allocated by jbd2_fc_get_buf
866	* for completion.
867	*/
868	int jbd2_fc_wait_bufs(journal_t journal, int* num_blks)
869	{
870	struct buffer_head *bh;
871	int i, j_fc_off;
872
873	j_fc_off = journal->j_fc_off;
874
875	/*
876	* Wait in reverse order to minimize chances of us being woken up before
877	* all IOs have completed
878	*/
879	for (i = j_fc_off - `1`; i >= j_fc_off - num_blks; i--) {
880	bh = journal->j_fc_wbuf[i];
881	wait_on_buffer(bh);
882	/*
883	* Update j_fc_off so jbd2_fc_release_bufs can release remain
884	* buffer head.
885	*/
886	if (unlikely(!buffer_uptodate(bh))) {
887	journal->j_fc_off = i + `1`;
888	return -EIO;
889	}
890	put_bh(bh);
891	journal->j_fc_wbuf[i] = NULL;
892	}
893
894	return `0`;
895	}
896	EXPORT_SYMBOL(jbd2_fc_wait_bufs);
897
898	void jbd2_fc_release_bufs(journal_t *journal)
899	{
900	struct buffer_head *bh;
901	int i, j_fc_off;
902
903	j_fc_off = journal->j_fc_off;
904
905	for (i = j_fc_off - `1`; i >= `0`; i--) {
906	bh = journal->j_fc_wbuf[i];
907	if (!bh)
908	break;
909	put_bh(bh);
910	journal->j_fc_wbuf[i] = NULL;
911	}
912	}
913	EXPORT_SYMBOL(jbd2_fc_release_bufs);
914
915	/*
916	* Conversion of logical to physical block numbers for the journal
917	*
918	* On external journals the journal blocks are identity-mapped, so
919	* this is a no-op. If needed, we can use j_blk_offset - everything is
920	* ready.
921	*/
922	int jbd2_journal_bmap(journal_t journal, unsigned* long blocknr,
923	unsigned long long *retp)
924	{
925	int err = `0`;
926	unsigned long long ret;
927	sector_t block = blocknr;
928
929	if (journal->j_bmap) {
930	err = journal->j_bmap(journal, &block);
931	if (err == `0`)
932	*retp = block;
933	} else if (journal->j_inode) {
934	ret = bmap(inode: journal->j_inode, block: &block);
935
936	if (ret \|\| !block) {
937	printk(KERN_ALERT "%s: journal block not found "
938	"at offset %lu on %s\n",
939	__func__, blocknr, journal->j_devname);
940	err = -EIO;
941	jbd2_journal_abort(journal, err);
942	} else {
943	*retp = block;
944	}
945
946	} else {
947	retp = blocknr; /* +journal->j_blk_offset /
948	}
949	return err;
950	}
951
952	/*
953	* We play buffer_head aliasing tricks to write data/metadata blocks to
954	* the journal without copying their contents, but for journal
955	* descriptor blocks we do need to generate bona fide buffers.
956	*
957	* After the caller of jbd2_journal_get_descriptor_buffer() has finished modifying
958	* the buffer's contents they really should run flush_dcache_folio(bh->b_folio).
959	* But we don't bother doing that, so there will be coherency problems with
960	* mmaps of blockdevs which hold live JBD-controlled filesystems.
961	*/
962	struct buffer_head *
963	jbd2_journal_get_descriptor_buffer(transaction_t transaction, int* type)
964	{
965	journal_t *journal = transaction->t_journal;
966	struct buffer_head *bh;
967	unsigned long long blocknr;
968	journal_header_t *header;
969	int err;
970
971	err = jbd2_journal_next_log_block(journal, retp: &blocknr);
972
973	if (err)
974	return NULL;
975
976	bh = __getblk(bdev: journal->j_dev, block: blocknr, size: journal->j_blocksize);
977	if (!bh)
978	return NULL;
979	atomic_dec(v: &transaction->t_outstanding_credits);
980	lock_buffer(bh);
981	memset(s: bh->b_data, c: `0`, n: journal->j_blocksize);
982	header = (journal_header_t *)bh->b_data;
983	header->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
984	header->h_blocktype = cpu_to_be32(type);
985	header->h_sequence = cpu_to_be32(transaction->t_tid);
986	set_buffer_uptodate(bh);
987	unlock_buffer(bh);
988	BUFFER_TRACE(bh, "return this buffer");
989	return bh;
990	}
991
992	void jbd2_descriptor_block_csum_set(journal_t j, struct* buffer_head *bh)
993	{
994	struct jbd2_journal_block_tail *tail;
995	__u32 csum;
996
997	if (!jbd2_journal_has_csum_v2or3(journal: j))
998	return;
999
1000	tail = (struct jbd2_journal_block_tail *)(bh->b_data + j->j_blocksize -
1001	sizeof(struct jbd2_journal_block_tail));
1002	tail->t_checksum = `0`;
1003	csum = jbd2_chksum(crc: j->j_csum_seed, address: bh->b_data, length: j->j_blocksize);
1004	tail->t_checksum = cpu_to_be32(csum);
1005	}
1006
1007	/*
1008	* Return tid of the oldest transaction in the journal and block in the journal
1009	* where the transaction starts.
1010	*
1011	* If the journal is now empty, return which will be the next transaction ID
1012	* we will write and where will that transaction start.
1013	*
1014	* The return value is 0 if journal tail cannot be pushed any further, 1 if
1015	* it can.
1016	*/
1017	int jbd2_journal_get_log_tail(journal_t journal, tid_t tid,
1018	unsigned long *block)
1019	{
1020	transaction_t *transaction;
1021	int ret;
1022
1023	read_lock(&journal->j_state_lock);
1024	spin_lock(lock: &journal->j_list_lock);
1025	transaction = journal->j_checkpoint_transactions;
1026	if (transaction) {
1027	*tid = transaction->t_tid;
1028	*block = transaction->t_log_start;
1029	} else if ((transaction = journal->j_committing_transaction) != NULL) {
1030	*tid = transaction->t_tid;
1031	*block = transaction->t_log_start;
1032	} else if ((transaction = journal->j_running_transaction) != NULL) {
1033	*tid = transaction->t_tid;
1034	*block = journal->j_head;
1035	} else {
1036	*tid = journal->j_transaction_sequence;
1037	*block = journal->j_head;
1038	}
1039	ret = tid_gt(x: *tid, y: journal->j_tail_sequence);
1040	spin_unlock(lock: &journal->j_list_lock);
1041	read_unlock(&journal->j_state_lock);
1042
1043	return ret;
1044	}
1045
1046	/*
1047	* Update information in journal structure and in on disk journal superblock
1048	* about log tail. This function does not check whether information passed in
1049	* really pushes log tail further. It's responsibility of the caller to make
1050	* sure provided log tail information is valid (e.g. by holding
1051	* j_checkpoint_mutex all the time between computing log tail and calling this
1052	* function as is the case with jbd2_cleanup_journal_tail()).
1053	*
1054	* Requires j_checkpoint_mutex
1055	*/
1056	int __jbd2_update_log_tail(journal_t journal, tid_t tid, unsigned* long block)
1057	{
1058	unsigned long freed;
1059	int ret;
1060
1061	BUG_ON(!mutex_is_locked(&journal->j_checkpoint_mutex));
1062
1063	/*
1064	* We cannot afford for write to remain in drive's caches since as
1065	* soon as we update j_tail, next transaction can start reusing journal
1066	* space and if we lose sb update during power failure we'd replay
1067	* old transaction with possibly newly overwritten data.
1068	*/
1069	ret = jbd2_journal_update_sb_log_tail(journal, tid, block, REQ_FUA);
1070	if (ret)
1071	goto out;
1072
1073	write_lock(&journal->j_state_lock);
1074	freed = block - journal->j_tail;
1075	if (block < journal->j_tail)
1076	freed += journal->j_last - journal->j_first;
1077
1078	trace_jbd2_update_log_tail(journal, first_tid: tid, block_nr: block, freed);
1079	jbd2_debug(`1`,
1080	"Cleaning journal tail from %u to %u (offset %lu), "
1081	"freeing %lu\n",
1082	journal->j_tail_sequence, tid, block, freed);
1083
1084	journal->j_free += freed;
1085	journal->j_tail_sequence = tid;
1086	journal->j_tail = block;
1087	write_unlock(&journal->j_state_lock);
1088
1089	out:
1090	return ret;
1091	}
1092
1093	/*
1094	* This is a variation of __jbd2_update_log_tail which checks for validity of
1095	* provided log tail and locks j_checkpoint_mutex. So it is safe against races
1096	* with other threads updating log tail.
1097	*/
1098	void jbd2_update_log_tail(journal_t journal, tid_t tid, unsigned* long block)
1099	{
1100	mutex_lock_io(lock: &journal->j_checkpoint_mutex);
1101	if (tid_gt(x: tid, y: journal->j_tail_sequence))
1102	__jbd2_update_log_tail(journal, tid, block);
1103	mutex_unlock(lock: &journal->j_checkpoint_mutex);
1104	}
1105
1106	struct jbd2_stats_proc_session {
1107	journal_t *journal;
1108	struct transaction_stats_s *stats;
1109	int start;
1110	int max;
1111	};
1112
1113	static void jbd2_seq_info_start(struct* seq_file seq, loff_t pos)
1114	{
1115	return *pos ? NULL : SEQ_START_TOKEN;
1116	}
1117
1118	static void jbd2_seq_info_next(struct* seq_file seq, void* v, loff_t pos)
1119	{
1120	(*pos)++;
1121	return NULL;
1122	}
1123
1124	static int jbd2_seq_info_show(struct seq_file seq, void* *v)
1125	{
1126	struct jbd2_stats_proc_session *s = seq->private;
1127
1128	if (v != SEQ_START_TOKEN)
1129	return `0`;
1130	seq_printf(m: seq, fmt: "%lu transactions (%lu requested), "
1131	"each up to %u blocks\n",
1132	s->stats->ts_tid, s->stats->ts_requested,
1133	s->journal->j_max_transaction_buffers);
1134	if (s->stats->ts_tid == `0`)
1135	return `0`;
1136	seq_printf(m: seq, fmt: "average: \n %ums waiting for transaction\n",
1137	jiffies_to_msecs(j: s->stats->run.rs_wait / s->stats->ts_tid));
1138	seq_printf(m: seq, fmt: " %ums request delay\n",
1139	(s->stats->ts_requested == `0`) ? `0` :
1140	jiffies_to_msecs(j: s->stats->run.rs_request_delay /
1141	s->stats->ts_requested));
1142	seq_printf(m: seq, fmt: " %ums running transaction\n",
1143	jiffies_to_msecs(j: s->stats->run.rs_running / s->stats->ts_tid));
1144	seq_printf(m: seq, fmt: " %ums transaction was being locked\n",
1145	jiffies_to_msecs(j: s->stats->run.rs_locked / s->stats->ts_tid));
1146	seq_printf(m: seq, fmt: " %ums flushing data (in ordered mode)\n",
1147	jiffies_to_msecs(j: s->stats->run.rs_flushing / s->stats->ts_tid));
1148	seq_printf(m: seq, fmt: " %ums logging transaction\n",
1149	jiffies_to_msecs(j: s->stats->run.rs_logging / s->stats->ts_tid));
1150	seq_printf(m: seq, fmt: " %lluus average transaction commit time\n",
1151	div_u64(dividend: s->journal->j_average_commit_time, divisor: `1000`));
1152	seq_printf(m: seq, fmt: " %lu handles per transaction\n",
1153	s->stats->run.rs_handle_count / s->stats->ts_tid);
1154	seq_printf(m: seq, fmt: " %lu blocks per transaction\n",
1155	s->stats->run.rs_blocks / s->stats->ts_tid);
1156	seq_printf(m: seq, fmt: " %lu logged blocks per transaction\n",
1157	s->stats->run.rs_blocks_logged / s->stats->ts_tid);
1158	return `0`;
1159	}
1160
1161	static void jbd2_seq_info_stop(struct seq_file seq, void* *v)
1162	{
1163	}
1164
1165	static const struct seq_operations jbd2_seq_info_ops = {
1166	.start = jbd2_seq_info_start,
1167	.next = jbd2_seq_info_next,
1168	.stop = jbd2_seq_info_stop,
1169	.show = jbd2_seq_info_show,
1170	};
1171
1172	static int jbd2_seq_info_open(struct inode inode, struct* file *file)
1173	{
1174	journal_t *journal = pde_data(inode);
1175	struct jbd2_stats_proc_session *s;
1176	int rc, size;
1177
1178	s = kmalloc(sizeof(*s), GFP_KERNEL);
1179	if (s == NULL)
1180	return -ENOMEM;
1181	size = sizeof(struct transaction_stats_s);
1182	s->stats = kmalloc(size, GFP_KERNEL);
1183	if (s->stats == NULL) {
1184	kfree(objp: s);
1185	return -ENOMEM;
1186	}
1187	spin_lock(lock: &journal->j_history_lock);
1188	memcpy(to: s->stats, from: &journal->j_stats, len: size);
1189	s->journal = journal;
1190	spin_unlock(lock: &journal->j_history_lock);
1191
1192	rc = seq_open(file, &jbd2_seq_info_ops);
1193	if (rc == `0`) {
1194	struct seq_file *m = file->private_data;
1195	m->private = s;
1196	} else {
1197	kfree(objp: s->stats);
1198	kfree(objp: s);
1199	}
1200	return rc;
1201
1202	}
1203
1204	static int jbd2_seq_info_release(struct inode inode, struct* file *file)
1205	{
1206	struct seq_file *seq = file->private_data;
1207	struct jbd2_stats_proc_session *s = seq->private;
1208	kfree(objp: s->stats);
1209	kfree(objp: s);
1210	return seq_release(inode, file);
1211	}
1212
1213	static const struct proc_ops jbd2_info_proc_ops = {
1214	.proc_open = jbd2_seq_info_open,
1215	.proc_read = seq_read,
1216	.proc_lseek = seq_lseek,
1217	.proc_release = jbd2_seq_info_release,
1218	};
1219
1220	static struct proc_dir_entry *proc_jbd2_stats;
1221
1222	static void jbd2_stats_proc_init(journal_t *journal)
1223	{
1224	journal->j_proc_entry = proc_mkdir(journal->j_devname, proc_jbd2_stats);
1225	if (journal->j_proc_entry) {
1226	proc_create_data("info", S_IRUGO, journal->j_proc_entry,
1227	&jbd2_info_proc_ops, journal);
1228	}
1229	}
1230
1231	static void jbd2_stats_proc_exit(journal_t *journal)
1232	{
1233	remove_proc_entry("info", journal->j_proc_entry);
1234	remove_proc_entry(journal->j_devname, proc_jbd2_stats);
1235	}
1236
1237	/ Minimum size of descriptor tag /
1238	static int jbd2_min_tag_size(void)
1239	{
1240	/*
1241	* Tag with 32-bit block numbers does not use last four bytes of the
1242	* structure
1243	*/
1244	return sizeof(journal_block_tag_t) - `4`;
1245	}
1246
1247	/**
1248	* jbd2_journal_shrink_scan()
1249	* @shrink: shrinker to work on
1250	* @sc: reclaim request to process
1251	*
1252	* Scan the checkpointed buffer on the checkpoint list and release the
1253	* journal_head.
1254	*/
1255	static unsigned long jbd2_journal_shrink_scan(struct shrinker *shrink,
1256	struct shrink_control *sc)
1257	{
1258	journal_t *journal = shrink->private_data;
1259	unsigned long nr_to_scan = sc->nr_to_scan;
1260	unsigned long nr_shrunk;
1261	unsigned long count;
1262
1263	count = percpu_counter_read_positive(fbc: &journal->j_checkpoint_jh_count);
1264	trace_jbd2_shrink_scan_enter(journal, nr_to_scan: sc->nr_to_scan, count);
1265
1266	nr_shrunk = jbd2_journal_shrink_checkpoint_list(journal, nr_to_scan: &nr_to_scan);
1267
1268	count = percpu_counter_read_positive(fbc: &journal->j_checkpoint_jh_count);
1269	trace_jbd2_shrink_scan_exit(journal, nr_to_scan, nr_shrunk, count);
1270
1271	return nr_shrunk;
1272	}
1273
1274	/**
1275	* jbd2_journal_shrink_count()
1276	* @shrink: shrinker to work on
1277	* @sc: reclaim request to process
1278	*
1279	* Count the number of checkpoint buffers on the checkpoint list.
1280	*/
1281	static unsigned long jbd2_journal_shrink_count(struct shrinker *shrink,
1282	struct shrink_control *sc)
1283	{
1284	journal_t *journal = shrink->private_data;
1285	unsigned long count;
1286
1287	count = percpu_counter_read_positive(fbc: &journal->j_checkpoint_jh_count);
1288	trace_jbd2_shrink_count(journal, nr_to_scan: sc->nr_to_scan, count);
1289
1290	return count;
1291	}
1292
1293	/*
1294	* If the journal init or create aborts, we need to mark the journal
1295	* superblock as being NULL to prevent the journal destroy from writing
1296	* back a bogus superblock.
1297	*/
1298	static void journal_fail_superblock(journal_t *journal)
1299	{
1300	struct buffer_head *bh = journal->j_sb_buffer;
1301	brelse(bh);
1302	journal->j_sb_buffer = NULL;
1303	}
1304
1305	/*
1306	* Check the superblock for a given journal, performing initial
1307	* validation of the format.
1308	*/
1309	static int journal_check_superblock(journal_t *journal)
1310	{
1311	journal_superblock_t *sb = journal->j_superblock;
1312	int num_fc_blks;
1313	int err = -EINVAL;
1314
1315	if (sb->s_header.h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER) \|\|
1316	sb->s_blocksize != cpu_to_be32(journal->j_blocksize)) {
1317	printk(KERN_WARNING "JBD2: no valid journal superblock found\n");
1318	return err;
1319	}
1320
1321	if (be32_to_cpu(sb->s_header.h_blocktype) != JBD2_SUPERBLOCK_V1 &&
1322	be32_to_cpu(sb->s_header.h_blocktype) != JBD2_SUPERBLOCK_V2) {
1323	printk(KERN_WARNING "JBD2: unrecognised superblock format ID\n");
1324	return err;
1325	}
1326
1327	if (be32_to_cpu(sb->s_maxlen) > journal->j_total_len) {
1328	printk(KERN_WARNING "JBD2: journal file too short\n");
1329	return err;
1330	}
1331
1332	if (be32_to_cpu(sb->s_first) == `0` \|\|
1333	be32_to_cpu(sb->s_first) >= journal->j_total_len) {
1334	printk(KERN_WARNING
1335	"JBD2: Invalid start block of journal: %u\n",
1336	be32_to_cpu(sb->s_first));
1337	return err;
1338	}
1339
1340	/*
1341	* If this is a V2 superblock, then we have to check the
1342	* features flags on it.
1343	*/
1344	if (!jbd2_format_support_feature(j: journal))
1345	return `0`;
1346
1347	if ((sb->s_feature_ro_compat &
1348	~cpu_to_be32(JBD2_KNOWN_ROCOMPAT_FEATURES)) \|\|
1349	(sb->s_feature_incompat &
1350	~cpu_to_be32(JBD2_KNOWN_INCOMPAT_FEATURES))) {
1351	printk(KERN_WARNING "JBD2: Unrecognised features on journal\n");
1352	return err;
1353	}
1354
1355	num_fc_blks = jbd2_has_feature_fast_commit(j: journal) ?
1356	jbd2_journal_get_num_fc_blks(jsb: sb) : `0`;
1357	if (be32_to_cpu(sb->s_maxlen) < JBD2_MIN_JOURNAL_BLOCKS \|\|
1358	be32_to_cpu(sb->s_maxlen) - JBD2_MIN_JOURNAL_BLOCKS < num_fc_blks) {
1359	printk(KERN_ERR "JBD2: journal file too short %u,%d\n",
1360	be32_to_cpu(sb->s_maxlen), num_fc_blks);
1361	return err;
1362	}
1363
1364	if (jbd2_has_feature_csum2(j: journal) &&
1365	jbd2_has_feature_csum3(j: journal)) {
1366	/ Can't have checksum v2 and v3 at the same time! /
1367	printk(KERN_ERR "JBD2: Can't enable checksumming v2 and v3 "
1368	"at the same time!\n");
1369	return err;
1370	}
1371
1372	if (jbd2_journal_has_csum_v2or3(journal) &&
1373	jbd2_has_feature_checksum(j: journal)) {
1374	/ Can't have checksum v1 and v2 on at the same time! /
1375	printk(KERN_ERR "JBD2: Can't enable checksumming v1 and v2/3 "
1376	"at the same time!\n");
1377	return err;
1378	}
1379
1380	if (jbd2_journal_has_csum_v2or3(journal)) {
1381	if (sb->s_checksum_type != JBD2_CRC32C_CHKSUM) {
1382	printk(KERN_ERR "JBD2: Unknown checksum type\n");
1383	return err;
1384	}
1385
1386	/ Check superblock checksum /
1387	if (sb->s_checksum != jbd2_superblock_csum(sb)) {
1388	printk(KERN_ERR "JBD2: journal checksum error\n");
1389	err = -EFSBADCRC;
1390	return err;
1391	}
1392	}
1393
1394	return `0`;
1395	}
1396
1397	static int journal_revoke_records_per_block(journal_t *journal)
1398	{
1399	int record_size;
1400	int space = journal->j_blocksize - sizeof(jbd2_journal_revoke_header_t);
1401
1402	if (jbd2_has_feature_64bit(j: journal))
1403	record_size = `8`;
1404	else
1405	record_size = `4`;
1406
1407	if (jbd2_journal_has_csum_v2or3(journal))
1408	space -= sizeof(struct jbd2_journal_block_tail);
1409	return space / record_size;
1410	}
1411
1412	static int jbd2_journal_get_max_txn_bufs(journal_t *journal)
1413	{
1414	return (journal->j_total_len - journal->j_fc_wbufsize) / `3`;
1415	}
1416
1417	/*
1418	* Base amount of descriptor blocks we reserve for each transaction.
1419	*/
1420	static int jbd2_descriptor_blocks_per_trans(journal_t *journal)
1421	{
1422	int tag_space = journal->j_blocksize - sizeof(journal_header_t);
1423	int tags_per_block;
1424
1425	/ Subtract UUID /
1426	tag_space -= `16`;
1427	if (jbd2_journal_has_csum_v2or3(journal))
1428	tag_space -= sizeof(struct jbd2_journal_block_tail);
1429	/ Commit code leaves a slack space of 16 bytes at the end of block /
1430	tags_per_block = (tag_space - `16`) / journal_tag_bytes(journal);
1431	/*
1432	* Revoke descriptors are accounted separately so we need to reserve
1433	* space for commit block and normal transaction descriptor blocks.
1434	*/
1435	return `1` + DIV_ROUND_UP(jbd2_journal_get_max_txn_bufs(journal),
1436	tags_per_block);
1437	}
1438
1439	/*
1440	* Initialize number of blocks each transaction reserves for its bookkeeping
1441	* and maximum number of blocks a transaction can use. This needs to be called
1442	* after the journal size and the fastcommit area size are initialized.
1443	*/
1444	static void jbd2_journal_init_transaction_limits(journal_t *journal)
1445	{
1446	journal->j_revoke_records_per_block =
1447	journal_revoke_records_per_block(journal);
1448	journal->j_transaction_overhead_buffers =
1449	jbd2_descriptor_blocks_per_trans(journal);
1450	journal->j_max_transaction_buffers =
1451	jbd2_journal_get_max_txn_bufs(journal);
1452	}
1453
1454	/*
1455	* Load the on-disk journal superblock and read the key fields into the
1456	* journal_t.
1457	*/
1458	static int journal_load_superblock(journal_t *journal)
1459	{
1460	int err;
1461	struct buffer_head *bh;
1462	journal_superblock_t *sb;
1463
1464	bh = getblk_unmovable(bdev: journal->j_dev, block: journal->j_blk_offset,
1465	size: journal->j_blocksize);
1466	if (bh)
1467	err = bh_read(bh, op_flags: `0`);
1468	if (!bh \|\| err < `0`) {
1469	pr_err("%s: Cannot read journal superblock\n", __func__);
1470	brelse(bh);
1471	return -EIO;
1472	}
1473
1474	journal->j_sb_buffer = bh;
1475	sb = (journal_superblock_t *)bh->b_data;
1476	journal->j_superblock = sb;
1477	err = journal_check_superblock(journal);
1478	if (err) {
1479	journal_fail_superblock(journal);
1480	return err;
1481	}
1482
1483	journal->j_tail_sequence = be32_to_cpu(sb->s_sequence);
1484	journal->j_tail = be32_to_cpu(sb->s_start);
1485	journal->j_first = be32_to_cpu(sb->s_first);
1486	journal->j_errno = be32_to_cpu(sb->s_errno);
1487	journal->j_last = be32_to_cpu(sb->s_maxlen);
1488
1489	if (be32_to_cpu(sb->s_maxlen) < journal->j_total_len)
1490	journal->j_total_len = be32_to_cpu(sb->s_maxlen);
1491	/ Precompute checksum seed for all metadata /
1492	if (jbd2_journal_has_csum_v2or3(journal))
1493	journal->j_csum_seed = jbd2_chksum(crc: ~`0`, address: sb->s_uuid,
1494	length: sizeof(sb->s_uuid));
1495	/ After journal features are set, we can compute transaction limits /
1496	jbd2_journal_init_transaction_limits(journal);
1497
1498	if (jbd2_has_feature_fast_commit(j: journal)) {
1499	journal->j_fc_last = be32_to_cpu(sb->s_maxlen);
1500	journal->j_last = journal->j_fc_last -
1501	jbd2_journal_get_num_fc_blks(jsb: sb);
1502	journal->j_fc_first = journal->j_last + `1`;
1503	journal->j_fc_off = `0`;
1504	}
1505
1506	return `0`;
1507	}
1508
1509
1510	/*
1511	* Management for journal control blocks: functions to create and
1512	* destroy journal_t structures, and to initialise and read existing
1513	* journal blocks from disk. */
1514
1515	/ The journal_init_common() function creates and fills a journal_t object*
1516	* in memory. It calls journal_load_superblock() to load the on-disk journal
1517	* superblock and initialize the journal_t object.
1518	*/
1519
1520	static journal_t journal_init_common(struct* block_device *bdev,
1521	struct block_device *fs_dev,
1522	unsigned long long start, int len, int blocksize)
1523	{
1524	static struct lock_class_key jbd2_trans_commit_key;
1525	journal_t *journal;
1526	int err;
1527	int n;
1528
1529	journal = kzalloc(sizeof(*journal), GFP_KERNEL);
1530	if (!journal)
1531	return ERR_PTR(error: -ENOMEM);
1532
1533	journal->j_blocksize = blocksize;
1534	journal->j_dev = bdev;
1535	journal->j_fs_dev = fs_dev;
1536	journal->j_blk_offset = start;
1537	journal->j_total_len = len;
1538	jbd2_init_fs_dev_write_error(journal);
1539
1540	err = journal_load_superblock(journal);
1541	if (err)
1542	goto err_cleanup;
1543
1544	init_waitqueue_head(&journal->j_wait_transaction_locked);
1545	init_waitqueue_head(&journal->j_wait_done_commit);
1546	init_waitqueue_head(&journal->j_wait_commit);
1547	init_waitqueue_head(&journal->j_wait_updates);
1548	init_waitqueue_head(&journal->j_wait_reserved);
1549	init_waitqueue_head(&journal->j_fc_wait);
1550	mutex_init(&journal->j_abort_mutex);
1551	mutex_init(&journal->j_barrier);
1552	mutex_init(&journal->j_checkpoint_mutex);
1553	spin_lock_init(&journal->j_revoke_lock);
1554	spin_lock_init(&journal->j_list_lock);
1555	spin_lock_init(&journal->j_history_lock);
1556	rwlock_init(&journal->j_state_lock);
1557
1558	journal->j_commit_interval = (HZ * JBD2_DEFAULT_MAX_COMMIT_AGE);
1559	journal->j_min_batch_time = `0`;
1560	journal->j_max_batch_time = `15000`; / 15ms /
1561	atomic_set(v: &journal->j_reserved_credits, i: `0`);
1562	lockdep_init_map(&journal->j_trans_commit_map, "jbd2_handle",
1563	&jbd2_trans_commit_key, `0`);
1564
1565	/ The journal is marked for error until we succeed with recovery! /
1566	journal->j_flags = JBD2_ABORT;
1567
1568	/ Set up a default-sized revoke table for the new mount. /
1569	err = jbd2_journal_init_revoke(journal, JOURNAL_REVOKE_DEFAULT_HASH);
1570	if (err)
1571	goto err_cleanup;
1572
1573	/*
1574	* journal descriptor can store up to n blocks, we need enough
1575	* buffers to write out full descriptor block.
1576	*/
1577	err = -ENOMEM;
1578	n = journal->j_blocksize / jbd2_min_tag_size();
1579	journal->j_wbufsize = n;
1580	journal->j_fc_wbuf = NULL;
1581	journal->j_wbuf = kmalloc_array(n, sizeof(struct buffer_head *),
1582	GFP_KERNEL);
1583	if (!journal->j_wbuf)
1584	goto err_cleanup;
1585
1586	err = percpu_counter_init(&journal->j_checkpoint_jh_count, `0`,
1587	GFP_KERNEL);
1588	if (err)
1589	goto err_cleanup;
1590
1591	journal->j_shrink_transaction = NULL;
1592
1593	journal->j_shrinker = shrinker_alloc(flags: `0`, fmt: "jbd2-journal:(%u:%u)",
1594	MAJOR(bdev->bd_dev),
1595	MINOR(bdev->bd_dev));
1596	if (!journal->j_shrinker) {
1597	err = -ENOMEM;
1598	goto err_cleanup;
1599	}
1600
1601	journal->j_shrinker->scan_objects = jbd2_journal_shrink_scan;
1602	journal->j_shrinker->count_objects = jbd2_journal_shrink_count;
1603	journal->j_shrinker->private_data = journal;
1604
1605	shrinker_register(shrinker: journal->j_shrinker);
1606
1607	return journal;
1608
1609	err_cleanup:
1610	percpu_counter_destroy(fbc: &journal->j_checkpoint_jh_count);
1611	kfree(objp: journal->j_wbuf);
1612	jbd2_journal_destroy_revoke(journal);
1613	journal_fail_superblock(journal);
1614	kfree(objp: journal);
1615	return ERR_PTR(error: err);
1616	}
1617
1618	/ jbd2_journal_init_dev and jbd2_journal_init_inode:*
1619	*
1620	* Create a journal structure assigned some fixed set of disk blocks to
1621	* the journal. We don't actually touch those disk blocks yet, but we
1622	* need to set up all of the mapping information to tell the journaling
1623	* system where the journal blocks are.
1624	*
1625	*/
1626
1627	/**
1628	* journal_t * jbd2_journal_init_dev() - creates and initialises a journal structure
1629	* @bdev: Block device on which to create the journal
1630	* @fs_dev: Device which hold journalled filesystem for this journal.
1631	* @start: Block nr Start of journal.
1632	* @len: Length of the journal in blocks.
1633	* @blocksize: blocksize of journalling device
1634	*
1635	* Returns: a newly created journal_t *
1636	*
1637	* jbd2_journal_init_dev creates a journal which maps a fixed contiguous
1638	* range of blocks on an arbitrary block device.
1639	*
1640	*/
1641	journal_t jbd2_journal_init_dev(struct* block_device *bdev,
1642	struct block_device *fs_dev,
1643	unsigned long long start, int len, int blocksize)
1644	{
1645	journal_t *journal;
1646
1647	journal = journal_init_common(bdev, fs_dev, start, len, blocksize);
1648	if (IS_ERR(ptr: journal))
1649	return ERR_CAST(ptr: journal);
1650
1651	snprintf(buf: journal->j_devname, size: sizeof(journal->j_devname),
1652	fmt: "%pg", journal->j_dev);
1653	strreplace(str: journal->j_devname, old: `'/'`, new: `'!'`);
1654	jbd2_stats_proc_init(journal);
1655
1656	return journal;
1657	}
1658
1659	/**
1660	* journal_t * jbd2_journal_init_inode () - creates a journal which maps to a inode.
1661	* @inode: An inode to create the journal in
1662	*
1663	* jbd2_journal_init_inode creates a journal which maps an on-disk inode as
1664	* the journal. The inode must exist already, must support bmap() and
1665	* must have all data blocks preallocated.
1666	*/
1667	journal_t jbd2_journal_init_inode(struct* inode *inode)
1668	{
1669	journal_t *journal;
1670	sector_t blocknr;
1671	int err = `0`;
1672
1673	blocknr = `0`;
1674	err = bmap(inode, block: &blocknr);
1675	if (err \|\| !blocknr) {
1676	pr_err("%s: Cannot locate journal superblock\n", __func__);
1677	return err ? ERR_PTR(error: err) : ERR_PTR(error: -EINVAL);
1678	}
1679
1680	jbd2_debug(`1`, "JBD2: inode %s/%ld, size %lld, bits %d, blksize %ld\n",
1681	inode->i_sb->s_id, inode->i_ino, (long long) inode->i_size,
1682	inode->i_sb->s_blocksize_bits, inode->i_sb->s_blocksize);
1683
1684	journal = journal_init_common(bdev: inode->i_sb->s_bdev, fs_dev: inode->i_sb->s_bdev,
1685	start: blocknr, len: inode->i_size >> inode->i_sb->s_blocksize_bits,
1686	blocksize: inode->i_sb->s_blocksize);
1687	if (IS_ERR(ptr: journal))
1688	return ERR_CAST(ptr: journal);
1689
1690	journal->j_inode = inode;
1691	snprintf(buf: journal->j_devname, size: sizeof(journal->j_devname),
1692	fmt: "%pg-%lu", journal->j_dev, journal->j_inode->i_ino);
1693	strreplace(str: journal->j_devname, old: `'/'`, new: `'!'`);
1694	jbd2_stats_proc_init(journal);
1695
1696	return journal;
1697	}
1698
1699	/*
1700	* Given a journal_t structure, initialise the various fields for
1701	* startup of a new journaling session. We use this both when creating
1702	* a journal, and after recovering an old journal to reset it for
1703	* subsequent use.
1704	*/
1705
1706	static int journal_reset(journal_t *journal)
1707	{
1708	journal_superblock_t *sb = journal->j_superblock;
1709	unsigned long long first, last;
1710
1711	first = be32_to_cpu(sb->s_first);
1712	last = be32_to_cpu(sb->s_maxlen);
1713	if (first + JBD2_MIN_JOURNAL_BLOCKS > last + `1`) {
1714	printk(KERN_ERR "JBD2: Journal too short (blocks %llu-%llu).\n",
1715	first, last);
1716	journal_fail_superblock(journal);
1717	return -EINVAL;
1718	}
1719
1720	journal->j_first = first;
1721	journal->j_last = last;
1722
1723	if (journal->j_head != `0` && journal->j_flags & JBD2_CYCLE_RECORD) {
1724	/*
1725	* Disable the cycled recording mode if the journal head block
1726	* number is not correct.
1727	*/
1728	if (journal->j_head < first \|\| journal->j_head >= last) {
1729	printk(KERN_WARNING "JBD2: Incorrect Journal head block %lu, "
1730	"disable journal_cycle_record\n",
1731	journal->j_head);
1732	journal->j_head = journal->j_first;
1733	}
1734	} else {
1735	journal->j_head = journal->j_first;
1736	}
1737	journal->j_tail = journal->j_head;
1738	journal->j_free = journal->j_last - journal->j_first;
1739
1740	journal->j_tail_sequence = journal->j_transaction_sequence;
1741	journal->j_commit_sequence = journal->j_transaction_sequence - `1`;
1742	journal->j_commit_request = journal->j_commit_sequence;
1743
1744	/*
1745	* Now that journal recovery is done, turn fast commits off here. This
1746	* way, if fast commit was enabled before the crash but if now FS has
1747	* disabled it, we don't enable fast commits.
1748	*/
1749	jbd2_clear_feature_fast_commit(j: journal);
1750
1751	/*
1752	* As a special case, if the on-disk copy is already marked as needing
1753	* no recovery (s_start == 0), then we can safely defer the superblock
1754	* update until the next commit by setting JBD2_FLUSHED. This avoids
1755	* attempting a write to a potential-readonly device.
1756	*/
1757	if (sb->s_start == `0`) {
1758	jbd2_debug(`1`, "JBD2: Skipping superblock update on recovered sb "
1759	"(start %ld, seq %u, errno %d)\n",
1760	journal->j_tail, journal->j_tail_sequence,
1761	journal->j_errno);
1762	journal->j_flags \|= JBD2_FLUSHED;
1763	} else {
1764	/ Lock here to make assertions happy... /
1765	mutex_lock_io(lock: &journal->j_checkpoint_mutex);
1766	/*
1767	* Update log tail information. We use REQ_FUA since new
1768	* transaction will start reusing journal space and so we
1769	* must make sure information about current log tail is on
1770	* disk before that.
1771	*/
1772	jbd2_journal_update_sb_log_tail(journal,
1773	journal->j_tail_sequence,
1774	journal->j_tail, REQ_FUA);
1775	mutex_unlock(lock: &journal->j_checkpoint_mutex);
1776	}
1777	return jbd2_journal_start_thread(journal);
1778	}
1779
1780	/*
1781	* This function expects that the caller will have locked the journal
1782	* buffer head, and will return with it unlocked
1783	*/
1784	static int jbd2_write_superblock(journal_t *journal, blk_opf_t write_flags)
1785	{
1786	struct buffer_head *bh = journal->j_sb_buffer;
1787	journal_superblock_t *sb = journal->j_superblock;
1788	int ret = `0`;
1789
1790	/ Buffer got discarded which means block device got invalidated /
1791	if (!buffer_mapped(bh)) {
1792	unlock_buffer(bh);
1793	return -EIO;
1794	}
1795
1796	/*
1797	* Always set high priority flags to exempt from block layer's
1798	* QOS policies, e.g. writeback throttle.
1799	*/
1800	write_flags \|= JBD2_JOURNAL_REQ_FLAGS;
1801	if (!(journal->j_flags & JBD2_BARRIER))
1802	write_flags &= ~(REQ_FUA \| REQ_PREFLUSH);
1803
1804	trace_jbd2_write_superblock(journal, write_flags);
1805
1806	if (buffer_write_io_error(bh)) {
1807	/*
1808	* Oh, dear. A previous attempt to write the journal
1809	* superblock failed. This could happen because the
1810	* USB device was yanked out. Or it could happen to
1811	* be a transient write error and maybe the block will
1812	* be remapped. Nothing we can do but to retry the
1813	* write and hope for the best.
1814	*/
1815	printk(KERN_ERR "JBD2: previous I/O error detected "
1816	"for journal superblock update for %s.\n",
1817	journal->j_devname);
1818	clear_buffer_write_io_error(bh);
1819	set_buffer_uptodate(bh);
1820	}
1821	if (jbd2_journal_has_csum_v2or3(journal))
1822	sb->s_checksum = jbd2_superblock_csum(sb);
1823	get_bh(bh);
1824	bh->b_end_io = end_buffer_write_sync;
1825	submit_bh(REQ_OP_WRITE \| write_flags, bh);
1826	wait_on_buffer(bh);
1827	if (buffer_write_io_error(bh)) {
1828	clear_buffer_write_io_error(bh);
1829	set_buffer_uptodate(bh);
1830	ret = -EIO;
1831	}
1832	if (ret) {
1833	printk(KERN_ERR "JBD2: I/O error when updating journal superblock for %s.\n",
1834	journal->j_devname);
1835	if (!is_journal_aborted(journal))
1836	jbd2_journal_abort(journal, ret);
1837	}
1838
1839	return ret;
1840	}
1841
1842	/**
1843	* jbd2_journal_update_sb_log_tail() - Update log tail in journal sb on disk.
1844	* @journal: The journal to update.
1845	* @tail_tid: TID of the new transaction at the tail of the log
1846	* @tail_block: The first block of the transaction at the tail of the log
1847	* @write_flags: Flags for the journal sb write operation
1848	*
1849	* Update a journal's superblock information about log tail and write it to
1850	* disk, waiting for the IO to complete.
1851	*/
1852	int jbd2_journal_update_sb_log_tail(journal_t *journal, tid_t tail_tid,
1853	unsigned long tail_block,
1854	blk_opf_t write_flags)
1855	{
1856	journal_superblock_t *sb = journal->j_superblock;
1857	int ret;
1858
1859	if (is_journal_aborted(journal))
1860	return -EIO;
1861	if (jbd2_check_fs_dev_write_error(journal)) {
1862	jbd2_journal_abort(journal, -EIO);
1863	return -EIO;
1864	}
1865
1866	BUG_ON(!mutex_is_locked(&journal->j_checkpoint_mutex));
1867	jbd2_debug(`1`, "JBD2: updating superblock (start %lu, seq %u)\n",
1868	tail_block, tail_tid);
1869
1870	lock_buffer(bh: journal->j_sb_buffer);
1871	sb->s_sequence = cpu_to_be32(tail_tid);
1872	sb->s_start = cpu_to_be32(tail_block);
1873
1874	ret = jbd2_write_superblock(journal, write_flags);
1875	if (ret)
1876	goto out;
1877
1878	/ Log is no longer empty /
1879	write_lock(&journal->j_state_lock);
1880	journal->j_flags &= ~JBD2_FLUSHED;
1881	write_unlock(&journal->j_state_lock);
1882
1883	out:
1884	return ret;
1885	}
1886
1887	/**
1888	* jbd2_mark_journal_empty() - Mark on disk journal as empty.
1889	* @journal: The journal to update.
1890	* @write_flags: Flags for the journal sb write operation
1891	*
1892	* Update a journal's dynamic superblock fields to show that journal is empty.
1893	* Write updated superblock to disk waiting for IO to complete.
1894	*/
1895	static void jbd2_mark_journal_empty(journal_t *journal, blk_opf_t write_flags)
1896	{
1897	journal_superblock_t *sb = journal->j_superblock;
1898	bool had_fast_commit = false;
1899
1900	BUG_ON(!mutex_is_locked(&journal->j_checkpoint_mutex));
1901	lock_buffer(bh: journal->j_sb_buffer);
1902	if (sb->s_start == `0`) { / Is it already empty? /
1903	unlock_buffer(bh: journal->j_sb_buffer);
1904	return;
1905	}
1906
1907	jbd2_debug(`1`, "JBD2: Marking journal as empty (seq %u)\n",
1908	journal->j_tail_sequence);
1909
1910	sb->s_sequence = cpu_to_be32(journal->j_tail_sequence);
1911	sb->s_start = cpu_to_be32(`0`);
1912	sb->s_head = cpu_to_be32(journal->j_head);
1913	if (jbd2_has_feature_fast_commit(j: journal)) {
1914	/*
1915	* When journal is clean, no need to commit fast commit flag and
1916	* make file system incompatible with older kernels.
1917	*/
1918	jbd2_clear_feature_fast_commit(j: journal);
1919	had_fast_commit = true;
1920	}
1921
1922	jbd2_write_superblock(journal, write_flags);
1923
1924	if (had_fast_commit)
1925	jbd2_set_feature_fast_commit(j: journal);
1926
1927	/ Log is empty /
1928	write_lock(&journal->j_state_lock);
1929	journal->j_flags \|= JBD2_FLUSHED;
1930	write_unlock(&journal->j_state_lock);
1931	}
1932
1933	/**
1934	* __jbd2_journal_erase() - Discard or zeroout journal blocks (excluding superblock)
1935	* @journal: The journal to erase.
1936	* @flags: A discard/zeroout request is sent for each physically contigous
1937	* region of the journal. Either JBD2_JOURNAL_FLUSH_DISCARD or
1938	* JBD2_JOURNAL_FLUSH_ZEROOUT must be set to determine which operation
1939	* to perform.
1940	*
1941	* Note: JBD2_JOURNAL_FLUSH_ZEROOUT attempts to use hardware offload. Zeroes
1942	* will be explicitly written if no hardware offload is available, see
1943	* blkdev_issue_zeroout for more details.
1944	*/
1945	static int __jbd2_journal_erase(journal_t journal, unsigned* int flags)
1946	{
1947	int err = `0`;
1948	unsigned long block, log_offset; / logical /
1949	unsigned long long phys_block, block_start, block_stop; / physical /
1950	loff_t byte_start, byte_stop, byte_count;
1951
1952	/ flags must be set to either discard or zeroout /
1953	if ((flags & ~JBD2_JOURNAL_FLUSH_VALID) \|\| !flags \|\|
1954	((flags & JBD2_JOURNAL_FLUSH_DISCARD) &&
1955	(flags & JBD2_JOURNAL_FLUSH_ZEROOUT)))
1956	return -EINVAL;
1957
1958	if ((flags & JBD2_JOURNAL_FLUSH_DISCARD) &&
1959	!bdev_max_discard_sectors(bdev: journal->j_dev))
1960	return -EOPNOTSUPP;
1961
1962	/*
1963	* lookup block mapping and issue discard/zeroout for each
1964	* contiguous region
1965	*/
1966	log_offset = be32_to_cpu(journal->j_superblock->s_first);
1967	block_start = ~`0ULL`;
1968	for (block = log_offset; block < journal->j_total_len; block++) {
1969	err = jbd2_journal_bmap(journal, blocknr: block, retp: &phys_block);
1970	if (err) {
1971	pr_err("JBD2: bad block at offset %lu", block);
1972	return err;
1973	}
1974
1975	if (block_start == ~`0ULL`)
1976	block_stop = block_start = phys_block;
1977
1978	/*
1979	* last block not contiguous with current block,
1980	* process last contiguous region and return to this block on
1981	* next loop
1982	*/
1983	if (phys_block != block_stop) {
1984	block--;
1985	} else {
1986	block_stop++;
1987	/*
1988	* if this isn't the last block of journal,
1989	* no need to process now because next block may also
1990	* be part of this contiguous region
1991	*/
1992	if (block != journal->j_total_len - `1`)
1993	continue;
1994	}
1995
1996	/*
1997	* end of contiguous region or this is last block of journal,
1998	* take care of the region
1999	*/
2000	byte_start = block_start * journal->j_blocksize;
2001	byte_stop = block_stop * journal->j_blocksize;
2002	byte_count = (block_stop - block_start) * journal->j_blocksize;
2003
2004	truncate_inode_pages_range(journal->j_dev->bd_mapping,
2005	lstart: byte_start, lend: byte_stop - `1`);
2006
2007	if (flags & JBD2_JOURNAL_FLUSH_DISCARD) {
2008	err = blkdev_issue_discard(bdev: journal->j_dev,
2009	sector: byte_start >> SECTOR_SHIFT,
2010	nr_sects: byte_count >> SECTOR_SHIFT,
2011	GFP_NOFS);
2012	} else if (flags & JBD2_JOURNAL_FLUSH_ZEROOUT) {
2013	err = blkdev_issue_zeroout(bdev: journal->j_dev,
2014	sector: byte_start >> SECTOR_SHIFT,
2015	nr_sects: byte_count >> SECTOR_SHIFT,
2016	GFP_NOFS, flags: `0`);
2017	}
2018
2019	if (unlikely(err != `0`)) {
2020	pr_err("JBD2: (error %d) unable to wipe journal at physical blocks [%llu, %llu)",
2021	err, block_start, block_stop);
2022	return err;
2023	}
2024
2025	/ reset start and stop after processing a region /
2026	block_start = ~`0ULL`;
2027	}
2028
2029	return blkdev_issue_flush(bdev: journal->j_dev);
2030	}
2031
2032	/**
2033	* jbd2_journal_update_sb_errno() - Update error in the journal.
2034	* @journal: The journal to update.
2035	*
2036	* Update a journal's errno. Write updated superblock to disk waiting for IO
2037	* to complete.
2038	*/
2039	void jbd2_journal_update_sb_errno(journal_t *journal)
2040	{
2041	journal_superblock_t *sb = journal->j_superblock;
2042	int errcode;
2043
2044	lock_buffer(bh: journal->j_sb_buffer);
2045	errcode = journal->j_errno;
2046	if (errcode == -ESHUTDOWN)
2047	errcode = `0`;
2048	jbd2_debug(`1`, "JBD2: updating superblock error (errno %d)\n", errcode);
2049	sb->s_errno = cpu_to_be32(errcode);
2050
2051	jbd2_write_superblock(journal, REQ_FUA);
2052	}
2053	EXPORT_SYMBOL(jbd2_journal_update_sb_errno);
2054
2055	/**
2056	* jbd2_journal_load() - Read journal from disk.
2057	* @journal: Journal to act on.
2058	*
2059	* Given a journal_t structure which tells us which disk blocks contain
2060	* a journal, read the journal from disk to initialise the in-memory
2061	* structures.
2062	*/
2063	int jbd2_journal_load(journal_t *journal)
2064	{
2065	int err;
2066	journal_superblock_t *sb = journal->j_superblock;
2067
2068	/*
2069	* Create a slab for this blocksize
2070	*/
2071	err = jbd2_journal_create_slab(be32_to_cpu(sb->s_blocksize));
2072	if (err)
2073	return err;
2074
2075	/ Let the recovery code check whether it needs to recover any*
2076	* data from the journal. */
2077	err = jbd2_journal_recover(journal);
2078	if (err) {
2079	pr_warn("JBD2: journal recovery failed\n");
2080	return err;
2081	}
2082
2083	if (journal->j_failed_commit) {
2084	printk(KERN_ERR "JBD2: journal transaction %u on %s "
2085	"is corrupt.\n", journal->j_failed_commit,
2086	journal->j_devname);
2087	return -EFSCORRUPTED;
2088	}
2089	/*
2090	* clear JBD2_ABORT flag initialized in journal_init_common
2091	* here to update log tail information with the newest seq.
2092	*/
2093	journal->j_flags &= ~JBD2_ABORT;
2094
2095	/ OK, we've finished with the dynamic journal bits:*
2096	* reinitialise the dynamic contents of the superblock in memory
2097	* and reset them on disk. */
2098	err = journal_reset(journal);
2099	if (err) {
2100	pr_warn("JBD2: journal reset failed\n");
2101	return err;
2102	}
2103
2104	journal->j_flags \|= JBD2_LOADED;
2105	return `0`;
2106	}
2107
2108	/**
2109	* jbd2_journal_destroy() - Release a journal_t structure.
2110	* @journal: Journal to act on.
2111	*
2112	* Release a journal_t structure once it is no longer in use by the
2113	* journaled object.
2114	* Return <0 if we couldn't clean up the journal.
2115	*/
2116	int jbd2_journal_destroy(journal_t *journal)
2117	{
2118	int err = `0`;
2119
2120	/ Wait for the commit thread to wake up and die. /
2121	journal_kill_thread(journal);
2122
2123	/ Force a final log commit /
2124	if (journal->j_running_transaction)
2125	jbd2_journal_commit_transaction(journal);
2126
2127	/ Force any old transactions to disk /
2128
2129	/ Totally anal locking here... /
2130	spin_lock(lock: &journal->j_list_lock);
2131	while (journal->j_checkpoint_transactions != NULL) {
2132	spin_unlock(lock: &journal->j_list_lock);
2133	mutex_lock_io(lock: &journal->j_checkpoint_mutex);
2134	err = jbd2_log_do_checkpoint(journal);
2135	mutex_unlock(lock: &journal->j_checkpoint_mutex);
2136	/*
2137	* If checkpointing failed, just free the buffers to avoid
2138	* looping forever
2139	*/
2140	if (err) {
2141	jbd2_journal_destroy_checkpoint(journal);
2142	spin_lock(lock: &journal->j_list_lock);
2143	break;
2144	}
2145	spin_lock(lock: &journal->j_list_lock);
2146	}
2147
2148	J_ASSERT(journal->j_running_transaction == NULL);
2149	J_ASSERT(journal->j_committing_transaction == NULL);
2150	J_ASSERT(journal->j_checkpoint_transactions == NULL);
2151	spin_unlock(lock: &journal->j_list_lock);
2152
2153	/*
2154	* OK, all checkpoint transactions have been checked, now check the
2155	* writeback errseq of fs dev and abort the journal if some buffer
2156	* failed to write back to the original location, otherwise the
2157	* filesystem may become inconsistent.
2158	*/
2159	if (!is_journal_aborted(journal) &&
2160	jbd2_check_fs_dev_write_error(journal))
2161	jbd2_journal_abort(journal, -EIO);
2162
2163	if (journal->j_sb_buffer) {
2164	if (!is_journal_aborted(journal)) {
2165	mutex_lock_io(lock: &journal->j_checkpoint_mutex);
2166
2167	write_lock(&journal->j_state_lock);
2168	journal->j_tail_sequence =
2169	++journal->j_transaction_sequence;
2170	write_unlock(&journal->j_state_lock);
2171
2172	jbd2_mark_journal_empty(journal, REQ_PREFLUSH \| REQ_FUA);
2173	mutex_unlock(lock: &journal->j_checkpoint_mutex);
2174	} else
2175	err = -EIO;
2176	brelse(bh: journal->j_sb_buffer);
2177	}
2178
2179	if (journal->j_shrinker) {
2180	percpu_counter_destroy(fbc: &journal->j_checkpoint_jh_count);
2181	shrinker_free(shrinker: journal->j_shrinker);
2182	}
2183	if (journal->j_proc_entry)
2184	jbd2_stats_proc_exit(journal);
2185	iput(journal->j_inode);
2186	if (journal->j_revoke)
2187	jbd2_journal_destroy_revoke(journal);
2188	kfree(objp: journal->j_fc_wbuf);
2189	kfree(objp: journal->j_wbuf);
2190	kfree(objp: journal);
2191
2192	return err;
2193	}
2194
2195
2196	/**
2197	* jbd2_journal_check_used_features() - Check if features specified are used.
2198	* @journal: Journal to check.
2199	* @compat: bitmask of compatible features
2200	* @ro: bitmask of features that force read-only mount
2201	* @incompat: bitmask of incompatible features
2202	*
2203	* Check whether the journal uses all of a given set of
2204	* features. Return true (non-zero) if it does.
2205	**/
2206
2207	int jbd2_journal_check_used_features(journal_t journal, unsigned* long compat,
2208	unsigned long ro, unsigned long incompat)
2209	{
2210	journal_superblock_t *sb;
2211
2212	if (!compat && !ro && !incompat)
2213	return `1`;
2214	if (!jbd2_format_support_feature(j: journal))
2215	return `0`;
2216
2217	sb = journal->j_superblock;
2218
2219	if (((be32_to_cpu(sb->s_feature_compat) & compat) == compat) &&
2220	((be32_to_cpu(sb->s_feature_ro_compat) & ro) == ro) &&
2221	((be32_to_cpu(sb->s_feature_incompat) & incompat) == incompat))
2222	return `1`;
2223
2224	return `0`;
2225	}
2226
2227	/**
2228	* jbd2_journal_check_available_features() - Check feature set in journalling layer
2229	* @journal: Journal to check.
2230	* @compat: bitmask of compatible features
2231	* @ro: bitmask of features that force read-only mount
2232	* @incompat: bitmask of incompatible features
2233	*
2234	* Check whether the journaling code supports the use of
2235	* all of a given set of features on this journal. Return true
2236	* (non-zero) if it can. */
2237
2238	int jbd2_journal_check_available_features(journal_t journal, unsigned* long compat,
2239	unsigned long ro, unsigned long incompat)
2240	{
2241	if (!compat && !ro && !incompat)
2242	return `1`;
2243
2244	if (!jbd2_format_support_feature(j: journal))
2245	return `0`;
2246
2247	if ((compat & JBD2_KNOWN_COMPAT_FEATURES) == compat &&
2248	(ro & JBD2_KNOWN_ROCOMPAT_FEATURES) == ro &&
2249	(incompat & JBD2_KNOWN_INCOMPAT_FEATURES) == incompat)
2250	return `1`;
2251
2252	return `0`;
2253	}
2254
2255	static int
2256	jbd2_journal_initialize_fast_commit(journal_t *journal)
2257	{
2258	journal_superblock_t *sb = journal->j_superblock;
2259	unsigned long long num_fc_blks;
2260
2261	num_fc_blks = jbd2_journal_get_num_fc_blks(jsb: sb);
2262	if (journal->j_last - num_fc_blks < JBD2_MIN_JOURNAL_BLOCKS)
2263	return -ENOSPC;
2264
2265	/ Are we called twice? /
2266	WARN_ON(journal->j_fc_wbuf != NULL);
2267	journal->j_fc_wbuf = kmalloc_array(num_fc_blks,
2268	sizeof(struct buffer_head *), GFP_KERNEL);
2269	if (!journal->j_fc_wbuf)
2270	return -ENOMEM;
2271
2272	journal->j_fc_wbufsize = num_fc_blks;
2273	journal->j_fc_last = journal->j_last;
2274	journal->j_last = journal->j_fc_last - num_fc_blks;
2275	journal->j_fc_first = journal->j_last + `1`;
2276	journal->j_fc_off = `0`;
2277	journal->j_free = journal->j_last - journal->j_first;
2278
2279	return `0`;
2280	}
2281
2282	/**
2283	* jbd2_journal_set_features() - Mark a given journal feature in the superblock
2284	* @journal: Journal to act on.
2285	* @compat: bitmask of compatible features
2286	* @ro: bitmask of features that force read-only mount
2287	* @incompat: bitmask of incompatible features
2288	*
2289	* Mark a given journal feature as present on the
2290	* superblock. Returns true if the requested features could be set.
2291	*
2292	*/
2293
2294	int jbd2_journal_set_features(journal_t journal, unsigned* long compat,
2295	unsigned long ro, unsigned long incompat)
2296	{
2297	#define INCOMPAT_FEATURE_ON(f) \
2298	((incompat & (f)) && !(sb->s_feature_incompat & cpu_to_be32(f)))
2299	#define COMPAT_FEATURE_ON(f) \
2300	((compat & (f)) && !(sb->s_feature_compat & cpu_to_be32(f)))
2301	journal_superblock_t *sb;
2302
2303	if (jbd2_journal_check_used_features(journal, compat, ro, incompat))
2304	return `1`;
2305
2306	if (!jbd2_journal_check_available_features(journal, compat, ro, incompat))
2307	return `0`;
2308
2309	/ If enabling v2 checksums, turn on v3 instead /
2310	if (incompat & JBD2_FEATURE_INCOMPAT_CSUM_V2) {
2311	incompat &= ~JBD2_FEATURE_INCOMPAT_CSUM_V2;
2312	incompat \|= JBD2_FEATURE_INCOMPAT_CSUM_V3;
2313	}
2314
2315	/ Asking for checksumming v3 and v1? Only give them v3. /
2316	if (incompat & JBD2_FEATURE_INCOMPAT_CSUM_V3 &&
2317	compat & JBD2_FEATURE_COMPAT_CHECKSUM)
2318	compat &= ~JBD2_FEATURE_COMPAT_CHECKSUM;
2319
2320	jbd2_debug(`1`, "Setting new features 0x%lx/0x%lx/0x%lx\n",
2321	compat, ro, incompat);
2322
2323	sb = journal->j_superblock;
2324
2325	if (incompat & JBD2_FEATURE_INCOMPAT_FAST_COMMIT) {
2326	if (jbd2_journal_initialize_fast_commit(journal)) {
2327	pr_err("JBD2: Cannot enable fast commits.\n");
2328	return `0`;
2329	}
2330	}
2331
2332	lock_buffer(bh: journal->j_sb_buffer);
2333
2334	/ If enabling v3 checksums, update superblock and precompute seed /
2335	if (INCOMPAT_FEATURE_ON(JBD2_FEATURE_INCOMPAT_CSUM_V3)) {
2336	sb->s_checksum_type = JBD2_CRC32C_CHKSUM;
2337	sb->s_feature_compat &=
2338	~cpu_to_be32(JBD2_FEATURE_COMPAT_CHECKSUM);
2339	journal->j_csum_seed = jbd2_chksum(crc: ~`0`, address: sb->s_uuid,
2340	length: sizeof(sb->s_uuid));
2341	}
2342
2343	/ If enabling v1 checksums, downgrade superblock /
2344	if (COMPAT_FEATURE_ON(JBD2_FEATURE_COMPAT_CHECKSUM))
2345	sb->s_feature_incompat &=
2346	~cpu_to_be32(JBD2_FEATURE_INCOMPAT_CSUM_V2 \|
2347	JBD2_FEATURE_INCOMPAT_CSUM_V3);
2348
2349	sb->s_feature_compat \|= cpu_to_be32(compat);
2350	sb->s_feature_ro_compat \|= cpu_to_be32(ro);
2351	sb->s_feature_incompat \|= cpu_to_be32(incompat);
2352	unlock_buffer(bh: journal->j_sb_buffer);
2353	jbd2_journal_init_transaction_limits(journal);
2354
2355	return `1`;
2356	#undef COMPAT_FEATURE_ON
2357	#undef INCOMPAT_FEATURE_ON
2358	}
2359
2360	/*
2361	* jbd2_journal_clear_features() - Clear a given journal feature in the
2362	* superblock
2363	* @journal: Journal to act on.
2364	* @compat: bitmask of compatible features
2365	* @ro: bitmask of features that force read-only mount
2366	* @incompat: bitmask of incompatible features
2367	*
2368	* Clear a given journal feature as present on the
2369	* superblock.
2370	*/
2371	void jbd2_journal_clear_features(journal_t journal, unsigned* long compat,
2372	unsigned long ro, unsigned long incompat)
2373	{
2374	journal_superblock_t *sb;
2375
2376	jbd2_debug(`1`, "Clear features 0x%lx/0x%lx/0x%lx\n",
2377	compat, ro, incompat);
2378
2379	sb = journal->j_superblock;
2380
2381	sb->s_feature_compat &= ~cpu_to_be32(compat);
2382	sb->s_feature_ro_compat &= ~cpu_to_be32(ro);
2383	sb->s_feature_incompat &= ~cpu_to_be32(incompat);
2384	jbd2_journal_init_transaction_limits(journal);
2385	}
2386	EXPORT_SYMBOL(jbd2_journal_clear_features);
2387
2388	/**
2389	* jbd2_journal_flush() - Flush journal
2390	* @journal: Journal to act on.
2391	* @flags: optional operation on the journal blocks after the flush (see below)
2392	*
2393	* Flush all data for a given journal to disk and empty the journal.
2394	* Filesystems can use this when remounting readonly to ensure that
2395	* recovery does not need to happen on remount. Optionally, a discard or zeroout
2396	* can be issued on the journal blocks after flushing.
2397	*
2398	* flags:
2399	* JBD2_JOURNAL_FLUSH_DISCARD: issues discards for the journal blocks
2400	* JBD2_JOURNAL_FLUSH_ZEROOUT: issues zeroouts for the journal blocks
2401	*/
2402	int jbd2_journal_flush(journal_t journal, unsigned* int flags)
2403	{
2404	int err = `0`;
2405	transaction_t *transaction = NULL;
2406
2407	write_lock(&journal->j_state_lock);
2408
2409	/ Force everything buffered to the log... /
2410	if (journal->j_running_transaction) {
2411	transaction = journal->j_running_transaction;
2412	__jbd2_log_start_commit(journal, target: transaction->t_tid);
2413	} else if (journal->j_committing_transaction)
2414	transaction = journal->j_committing_transaction;
2415
2416	/ Wait for the log commit to complete... /
2417	if (transaction) {
2418	tid_t tid = transaction->t_tid;
2419
2420	write_unlock(&journal->j_state_lock);
2421	jbd2_log_wait_commit(journal, tid);
2422	} else {
2423	write_unlock(&journal->j_state_lock);
2424	}
2425
2426	/ ...and flush everything in the log out to disk. /
2427	spin_lock(lock: &journal->j_list_lock);
2428	while (!err && journal->j_checkpoint_transactions != NULL) {
2429	spin_unlock(lock: &journal->j_list_lock);
2430	mutex_lock_io(lock: &journal->j_checkpoint_mutex);
2431	err = jbd2_log_do_checkpoint(journal);
2432	mutex_unlock(lock: &journal->j_checkpoint_mutex);
2433	spin_lock(lock: &journal->j_list_lock);
2434	}
2435	spin_unlock(lock: &journal->j_list_lock);
2436
2437	if (is_journal_aborted(journal))
2438	return -EIO;
2439
2440	mutex_lock_io(lock: &journal->j_checkpoint_mutex);
2441	if (!err) {
2442	err = jbd2_cleanup_journal_tail(journal);
2443	if (err < `0`) {
2444	mutex_unlock(lock: &journal->j_checkpoint_mutex);
2445	goto out;
2446	}
2447	err = `0`;
2448	}
2449
2450	/ Finally, mark the journal as really needing no recovery.*
2451	* This sets s_start==0 in the underlying superblock, which is
2452	* the magic code for a fully-recovered superblock. Any future
2453	* commits of data to the journal will restore the current
2454	* s_start value. */
2455	jbd2_mark_journal_empty(journal, REQ_FUA);
2456
2457	if (flags)
2458	err = __jbd2_journal_erase(journal, flags);
2459
2460	mutex_unlock(lock: &journal->j_checkpoint_mutex);
2461	write_lock(&journal->j_state_lock);
2462	J_ASSERT(!journal->j_running_transaction);
2463	J_ASSERT(!journal->j_committing_transaction);
2464	J_ASSERT(!journal->j_checkpoint_transactions);
2465	J_ASSERT(journal->j_head == journal->j_tail);
2466	J_ASSERT(journal->j_tail_sequence == journal->j_transaction_sequence);
2467	write_unlock(&journal->j_state_lock);
2468	out:
2469	return err;
2470	}
2471
2472	/**
2473	* jbd2_journal_wipe() - Wipe journal contents
2474	* @journal: Journal to act on.
2475	* @write: flag (see below)
2476	*
2477	* Wipe out all of the contents of a journal, safely. This will produce
2478	* a warning if the journal contains any valid recovery information.
2479	* Must be called between journal_init_*() and jbd2_journal_load().
2480	*
2481	* If 'write' is non-zero, then we wipe out the journal on disk; otherwise
2482	* we merely suppress recovery.
2483	*/
2484
2485	int jbd2_journal_wipe(journal_t journal, int* write)
2486	{
2487	int err;
2488
2489	J_ASSERT (!(journal->j_flags & JBD2_LOADED));
2490
2491	if (!journal->j_tail)
2492	return `0`;
2493
2494	printk(KERN_WARNING "JBD2: %s recovery information on journal\n",
2495	write ? "Clearing" : "Ignoring");
2496
2497	err = jbd2_journal_skip_recovery(journal);
2498	if (write) {
2499	/ Lock to make assertions happy... /
2500	mutex_lock_io(lock: &journal->j_checkpoint_mutex);
2501	jbd2_mark_journal_empty(journal, REQ_FUA);
2502	mutex_unlock(lock: &journal->j_checkpoint_mutex);
2503	}
2504
2505	return err;
2506	}
2507
2508	/**
2509	* jbd2_journal_abort () - Shutdown the journal immediately.
2510	* @journal: the journal to shutdown.
2511	* @errno: an error number to record in the journal indicating
2512	* the reason for the shutdown.
2513	*
2514	* Perform a complete, immediate shutdown of the ENTIRE
2515	* journal (not of a single transaction). This operation cannot be
2516	* undone without closing and reopening the journal.
2517	*
2518	* The jbd2_journal_abort function is intended to support higher level error
2519	* recovery mechanisms such as the ext2/ext3 remount-readonly error
2520	* mode.
2521	*
2522	* Journal abort has very specific semantics. Any existing dirty,
2523	* unjournaled buffers in the main filesystem will still be written to
2524	* disk by bdflush, but the journaling mechanism will be suspended
2525	* immediately and no further transaction commits will be honoured.
2526	*
2527	* Any dirty, journaled buffers will be written back to disk without
2528	* hitting the journal. Atomicity cannot be guaranteed on an aborted
2529	* filesystem, but we _do_ attempt to leave as much data as possible
2530	* behind for fsck to use for cleanup.
2531	*
2532	* Any attempt to get a new transaction handle on a journal which is in
2533	* ABORT state will just result in an -EROFS error return. A
2534	* jbd2_journal_stop on an existing handle will return -EIO if we have
2535	* entered abort state during the update.
2536	*
2537	* Recursive transactions are not disturbed by journal abort until the
2538	* final jbd2_journal_stop, which will receive the -EIO error.
2539	*
2540	* Finally, the jbd2_journal_abort call allows the caller to supply an errno
2541	* which will be recorded (if possible) in the journal superblock. This
2542	* allows a client to record failure conditions in the middle of a
2543	* transaction without having to complete the transaction to record the
2544	* failure to disk. ext3_error, for example, now uses this
2545	* functionality.
2546	*
2547	*/
2548
2549	void jbd2_journal_abort(journal_t journal, int* errno)
2550	{
2551	transaction_t *transaction;
2552
2553	/*
2554	* Lock the aborting procedure until everything is done, this avoid
2555	* races between filesystem's error handling flow (e.g. ext4_abort()),
2556	* ensure panic after the error info is written into journal's
2557	* superblock.
2558	*/
2559	mutex_lock(lock: &journal->j_abort_mutex);
2560	/*
2561	* ESHUTDOWN always takes precedence because a file system check
2562	* caused by any other journal abort error is not required after
2563	* a shutdown triggered.
2564	*/
2565	write_lock(&journal->j_state_lock);
2566	if (journal->j_flags & JBD2_ABORT) {
2567	int old_errno = journal->j_errno;
2568
2569	write_unlock(&journal->j_state_lock);
2570	if (old_errno != -ESHUTDOWN && errno == -ESHUTDOWN) {
2571	journal->j_errno = errno;
2572	jbd2_journal_update_sb_errno(journal);
2573	}
2574	mutex_unlock(lock: &journal->j_abort_mutex);
2575	return;
2576	}
2577
2578	/*
2579	* Mark the abort as occurred and start current running transaction
2580	* to release all journaled buffer.
2581	*/
2582	pr_err("Aborting journal on device %s.\n", journal->j_devname);
2583
2584	journal->j_flags \|= JBD2_ABORT;
2585	journal->j_errno = errno;
2586	transaction = journal->j_running_transaction;
2587	if (transaction)
2588	__jbd2_log_start_commit(journal, target: transaction->t_tid);
2589	write_unlock(&journal->j_state_lock);
2590
2591	/*
2592	* Record errno to the journal super block, so that fsck and jbd2
2593	* layer could realise that a filesystem check is needed.
2594	*/
2595	jbd2_journal_update_sb_errno(journal);
2596	mutex_unlock(lock: &journal->j_abort_mutex);
2597	}
2598
2599	/**
2600	* jbd2_journal_errno() - returns the journal's error state.
2601	* @journal: journal to examine.
2602	*
2603	* This is the errno number set with jbd2_journal_abort(), the last
2604	* time the journal was mounted - if the journal was stopped
2605	* without calling abort this will be 0.
2606	*
2607	* If the journal has been aborted on this mount time -EROFS will
2608	* be returned.
2609	*/
2610	int jbd2_journal_errno(journal_t *journal)
2611	{
2612	int err;
2613
2614	read_lock(&journal->j_state_lock);
2615	if (journal->j_flags & JBD2_ABORT)
2616	err = -EROFS;
2617	else
2618	err = journal->j_errno;
2619	read_unlock(&journal->j_state_lock);
2620	return err;
2621	}
2622
2623	/**
2624	* jbd2_journal_clear_err() - clears the journal's error state
2625	* @journal: journal to act on.
2626	*
2627	* An error must be cleared or acked to take a FS out of readonly
2628	* mode.
2629	*/
2630	int jbd2_journal_clear_err(journal_t *journal)
2631	{
2632	int err = `0`;
2633
2634	write_lock(&journal->j_state_lock);
2635	if (journal->j_flags & JBD2_ABORT)
2636	err = -EROFS;
2637	else
2638	journal->j_errno = `0`;
2639	write_unlock(&journal->j_state_lock);
2640	return err;
2641	}
2642
2643	/**
2644	* jbd2_journal_ack_err() - Ack journal err.
2645	* @journal: journal to act on.
2646	*
2647	* An error must be cleared or acked to take a FS out of readonly
2648	* mode.
2649	*/
2650	void jbd2_journal_ack_err(journal_t *journal)
2651	{
2652	write_lock(&journal->j_state_lock);
2653	if (journal->j_errno)
2654	journal->j_flags \|= JBD2_ACK_ERR;
2655	write_unlock(&journal->j_state_lock);
2656	}
2657
2658	int jbd2_journal_blocks_per_folio(struct inode *inode)
2659	{
2660	return `1` << (PAGE_SHIFT + mapping_max_folio_order(mapping: inode->i_mapping) -
2661	inode->i_sb->s_blocksize_bits);
2662	}
2663
2664	/*
2665	* helper functions to deal with 32 or 64bit block numbers.
2666	*/
2667	size_t journal_tag_bytes(journal_t *journal)
2668	{
2669	size_t sz;
2670
2671	if (jbd2_has_feature_csum3(j: journal))
2672	return sizeof(journal_block_tag3_t);
2673
2674	sz = sizeof(journal_block_tag_t);
2675
2676	if (jbd2_has_feature_csum2(j: journal))
2677	sz += sizeof(__u16);
2678
2679	if (jbd2_has_feature_64bit(j: journal))
2680	return sz;
2681	else
2682	return sz - sizeof(__u32);
2683	}
2684
2685	/*
2686	* JBD memory management
2687	*
2688	* These functions are used to allocate block-sized chunks of memory
2689	* used for making copies of buffer_head data. Very often it will be
2690	* page-sized chunks of data, but sometimes it will be in
2691	* sub-page-size chunks. (For example, 16k pages on Power systems
2692	* with a 4k block file system.) For blocks smaller than a page, we
2693	* use a SLAB allocator. There are slab caches for each block size,
2694	* which are allocated at mount time, if necessary, and we only free
2695	* (all of) the slab caches when/if the jbd2 module is unloaded. For
2696	* this reason we don't need to a mutex to protect access to
2697	* jbd2_slab[] allocating or releasing memory; only in
2698	* jbd2_journal_create_slab().
2699	*/
2700	#define JBD2_MAX_SLABS 8
2701	static struct kmem_cache *jbd2_slab[JBD2_MAX_SLABS];
2702
2703	static const char *jbd2_slab_names[JBD2_MAX_SLABS] = {
2704	"jbd2_1k", "jbd2_2k", "jbd2_4k", "jbd2_8k",
2705	"jbd2_16k", "jbd2_32k", "jbd2_64k", "jbd2_128k"
2706	};
2707
2708
2709	static void jbd2_journal_destroy_slabs(void)
2710	{
2711	int i;
2712
2713	for (i = `0`; i < JBD2_MAX_SLABS; i++) {
2714	kmem_cache_destroy(s: jbd2_slab[i]);
2715	jbd2_slab[i] = NULL;
2716	}
2717	}
2718
2719	static int jbd2_journal_create_slab(size_t size)
2720	{
2721	static DEFINE_MUTEX(jbd2_slab_create_mutex);
2722	int i = order_base_2(size) - `10`;
2723	size_t slab_size;
2724
2725	if (size == PAGE_SIZE)
2726	return `0`;
2727
2728	if (i >= JBD2_MAX_SLABS)
2729	return -EINVAL;
2730
2731	if (unlikely(i < `0`))
2732	i = `0`;
2733	mutex_lock(lock: &jbd2_slab_create_mutex);
2734	if (jbd2_slab[i]) {
2735	mutex_unlock(lock: &jbd2_slab_create_mutex);
2736	return `0`; / Already created /
2737	}
2738
2739	slab_size = `1` << (i+`10`);
2740	jbd2_slab[i] = kmem_cache_create(jbd2_slab_names[i], slab_size,
2741	slab_size, `0`, NULL);
2742	mutex_unlock(lock: &jbd2_slab_create_mutex);
2743	if (!jbd2_slab[i]) {
2744	printk(KERN_EMERG "JBD2: no memory for jbd2_slab cache\n");
2745	return -ENOMEM;
2746	}
2747	return `0`;
2748	}
2749
2750	static struct kmem_cache *get_slab(size_t size)
2751	{
2752	int i = order_base_2(size) - `10`;
2753
2754	BUG_ON(i >= JBD2_MAX_SLABS);
2755	if (unlikely(i < `0`))
2756	i = `0`;
2757	BUG_ON(jbd2_slab[i] == NULL);
2758	return jbd2_slab[i];
2759	}
2760
2761	void *jbd2_alloc(size_t size, gfp_t flags)
2762	{
2763	void *ptr;
2764
2765	BUG_ON(size & (size-`1`)); / Must be a power of 2 /
2766
2767	if (size < PAGE_SIZE)
2768	ptr = kmem_cache_alloc(get_slab(size), flags);
2769	else
2770	ptr = (void *)__get_free_pages(flags, get_order(size));
2771
2772	/ Check alignment; SLUB has gotten this wrong in the past,*
2773	* and this can lead to user data corruption! */
2774	BUG_ON(((unsigned long) ptr) & (size-`1`));
2775
2776	return ptr;
2777	}
2778
2779	void jbd2_free(void *ptr, size_t size)
2780	{
2781	if (size < PAGE_SIZE)
2782	kmem_cache_free(s: get_slab(size), objp: ptr);
2783	else
2784	free_pages(addr: (unsigned long)ptr, order: get_order(size));
2785	};
2786
2787	/*
2788	* Journal_head storage management
2789	*/
2790	static struct kmem_cache *jbd2_journal_head_cache;
2791	#ifdef CONFIG_JBD2_DEBUG
2792	static atomic_t nr_journal_heads = ATOMIC_INIT(`0`);
2793	#endif
2794
2795	static int __init jbd2_journal_init_journal_head_cache(void)
2796	{
2797	J_ASSERT(!jbd2_journal_head_cache);
2798	jbd2_journal_head_cache = kmem_cache_create("jbd2_journal_head",
2799	sizeof(struct journal_head),
2800	`0`, / offset /
2801	SLAB_TEMPORARY \| SLAB_TYPESAFE_BY_RCU,
2802	NULL); / ctor /
2803	if (!jbd2_journal_head_cache) {
2804	printk(KERN_EMERG "JBD2: no memory for journal_head cache\n");
2805	return -ENOMEM;
2806	}
2807	return `0`;
2808	}
2809
2810	static void jbd2_journal_destroy_journal_head_cache(void)
2811	{
2812	kmem_cache_destroy(s: jbd2_journal_head_cache);
2813	jbd2_journal_head_cache = NULL;
2814	}
2815
2816	/*
2817	* journal_head splicing and dicing
2818	*/
2819	static struct journal_head journal_alloc_journal_head(void*)
2820	{
2821	struct journal_head *ret;
2822
2823	#ifdef CONFIG_JBD2_DEBUG
2824	atomic_inc(&nr_journal_heads);
2825	#endif
2826	ret = kmem_cache_zalloc(jbd2_journal_head_cache, GFP_NOFS);
2827	if (!ret) {
2828	jbd2_debug(`1`, "out of memory for journal_head\n");
2829	pr_notice_ratelimited("ENOMEM in %s, retrying.\n", __func__);
2830	ret = kmem_cache_zalloc(jbd2_journal_head_cache,
2831	GFP_NOFS \| __GFP_NOFAIL);
2832	}
2833	spin_lock_init(&ret->b_state_lock);
2834	return ret;
2835	}
2836
2837	static void journal_free_journal_head(struct journal_head *jh)
2838	{
2839	#ifdef CONFIG_JBD2_DEBUG
2840	atomic_dec(&nr_journal_heads);
2841	memset(jh, JBD2_POISON_FREE, sizeof(*jh));
2842	#endif
2843	kmem_cache_free(s: jbd2_journal_head_cache, objp: jh);
2844	}
2845
2846	/*
2847	* A journal_head is attached to a buffer_head whenever JBD has an
2848	* interest in the buffer.
2849	*
2850	* Whenever a buffer has an attached journal_head, its ->b_state:BH_JBD bit
2851	* is set. This bit is tested in core kernel code where we need to take
2852	* JBD-specific actions. Testing the zeroness of ->b_private is not reliable
2853	* there.
2854	*
2855	* When a buffer has its BH_JBD bit set, its ->b_count is elevated by one.
2856	*
2857	* When a buffer has its BH_JBD bit set it is immune from being released by
2858	* core kernel code, mainly via ->b_count.
2859	*
2860	* A journal_head is detached from its buffer_head when the journal_head's
2861	* b_jcount reaches zero. Running transaction (b_transaction) and checkpoint
2862	* transaction (b_cp_transaction) hold their references to b_jcount.
2863	*
2864	* Various places in the kernel want to attach a journal_head to a buffer_head
2865	* _before_ attaching the journal_head to a transaction. To protect the
2866	* journal_head in this situation, jbd2_journal_add_journal_head elevates the
2867	* journal_head's b_jcount refcount by one. The caller must call
2868	* jbd2_journal_put_journal_head() to undo this.
2869	*
2870	* So the typical usage would be:
2871	*
2872	* (Attach a journal_head if needed. Increments b_jcount)
2873	* struct journal_head *jh = jbd2_journal_add_journal_head(bh);
2874	* ...
2875	* (Get another reference for transaction)
2876	* jbd2_journal_grab_journal_head(bh);
2877	* jh->b_transaction = xxx;
2878	* (Put original reference)
2879	* jbd2_journal_put_journal_head(jh);
2880	*/
2881
2882	/*
2883	* Give a buffer_head a journal_head.
2884	*
2885	* May sleep.
2886	*/
2887	struct journal_head jbd2_journal_add_journal_head(struct* buffer_head *bh)
2888	{
2889	struct journal_head *jh;
2890	struct journal_head *new_jh = NULL;
2891
2892	repeat:
2893	if (!buffer_jbd(bh))
2894	new_jh = journal_alloc_journal_head();
2895
2896	jbd_lock_bh_journal_head(bh);
2897	if (buffer_jbd(bh)) {
2898	jh = bh2jh(bh);
2899	} else {
2900	J_ASSERT_BH(bh,
2901	(atomic_read(&bh->b_count) > `0`) \|\|
2902	(bh->b_folio && bh->b_folio->mapping));
2903
2904	if (!new_jh) {
2905	jbd_unlock_bh_journal_head(bh);
2906	goto repeat;
2907	}
2908
2909	jh = new_jh;
2910	new_jh = NULL; / We consumed it /
2911	set_buffer_jbd(bh);
2912	bh->b_private = jh;
2913	jh->b_bh = bh;
2914	get_bh(bh);
2915	BUFFER_TRACE(bh, "added journal_head");
2916	}
2917	jh->b_jcount++;
2918	jbd_unlock_bh_journal_head(bh);
2919	if (new_jh)
2920	journal_free_journal_head(jh: new_jh);
2921	return bh->b_private;
2922	}
2923
2924	/*
2925	* Grab a ref against this buffer_head's journal_head. If it ended up not
2926	* having a journal_head, return NULL
2927	*/
2928	struct journal_head jbd2_journal_grab_journal_head(struct* buffer_head *bh)
2929	{
2930	struct journal_head *jh = NULL;
2931
2932	jbd_lock_bh_journal_head(bh);
2933	if (buffer_jbd(bh)) {
2934	jh = bh2jh(bh);
2935	jh->b_jcount++;
2936	}
2937	jbd_unlock_bh_journal_head(bh);
2938	return jh;
2939	}
2940	EXPORT_SYMBOL(jbd2_journal_grab_journal_head);
2941
2942	static void __journal_remove_journal_head(struct buffer_head *bh)
2943	{
2944	struct journal_head *jh = bh2jh(bh);
2945
2946	J_ASSERT_JH(jh, jh->b_transaction == NULL);
2947	J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
2948	J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
2949	J_ASSERT_JH(jh, jh->b_jlist == BJ_None);
2950	J_ASSERT_BH(bh, buffer_jbd(bh));
2951	J_ASSERT_BH(bh, jh2bh(jh) == bh);
2952	BUFFER_TRACE(bh, "remove journal_head");
2953
2954	/ Unlink before dropping the lock /
2955	bh->b_private = NULL;
2956	jh->b_bh = NULL; / debug, really /
2957	clear_buffer_jbd(bh);
2958	}
2959
2960	static void journal_release_journal_head(struct journal_head *jh, size_t b_size)
2961	{
2962	if (jh->b_frozen_data) {
2963	printk(KERN_WARNING "%s: freeing b_frozen_data\n", __func__);
2964	jbd2_free(ptr: jh->b_frozen_data, size: b_size);
2965	}
2966	if (jh->b_committed_data) {
2967	printk(KERN_WARNING "%s: freeing b_committed_data\n", __func__);
2968	jbd2_free(ptr: jh->b_committed_data, size: b_size);
2969	}
2970	journal_free_journal_head(jh);
2971	}
2972
2973	/*
2974	* Drop a reference on the passed journal_head. If it fell to zero then
2975	* release the journal_head from the buffer_head.
2976	*/
2977	void jbd2_journal_put_journal_head(struct journal_head *jh)
2978	{
2979	struct buffer_head *bh = jh2bh(jh);
2980
2981	jbd_lock_bh_journal_head(bh);
2982	J_ASSERT_JH(jh, jh->b_jcount > `0`);
2983	--jh->b_jcount;
2984	if (!jh->b_jcount) {
2985	__journal_remove_journal_head(bh);
2986	jbd_unlock_bh_journal_head(bh);
2987	journal_release_journal_head(jh, b_size: bh->b_size);
2988	__brelse(bh);
2989	} else {
2990	jbd_unlock_bh_journal_head(bh);
2991	}
2992	}
2993	EXPORT_SYMBOL(jbd2_journal_put_journal_head);
2994
2995	/*
2996	* Initialize jbd inode head
2997	*/
2998	void jbd2_journal_init_jbd_inode(struct jbd2_inode jinode, struct* inode *inode)
2999	{
3000	jinode->i_transaction = NULL;
3001	jinode->i_next_transaction = NULL;
3002	jinode->i_vfs_inode = inode;
3003	jinode->i_flags = `0`;
3004	jinode->i_dirty_start = `0`;
3005	jinode->i_dirty_end = `0`;
3006	INIT_LIST_HEAD(list: &jinode->i_list);
3007	}
3008
3009	/*
3010	* Function to be called before we start removing inode from memory (i.e.,
3011	* clear_inode() is a fine place to be called from). It removes inode from
3012	* transaction's lists.
3013	*/
3014	void jbd2_journal_release_jbd_inode(journal_t *journal,
3015	struct jbd2_inode *jinode)
3016	{
3017	if (!journal)
3018	return;
3019	restart:
3020	spin_lock(lock: &journal->j_list_lock);
3021	/ Is commit writing out inode - we have to wait /
3022	if (jinode->i_flags & JI_COMMIT_RUNNING) {
3023	wait_queue_head_t *wq;
3024	DEFINE_WAIT_BIT(wait, &jinode->i_flags, __JI_COMMIT_RUNNING);
3025	wq = bit_waitqueue(word: &jinode->i_flags, __JI_COMMIT_RUNNING);
3026	prepare_to_wait(wq_head: wq, wq_entry: &wait.wq_entry, TASK_UNINTERRUPTIBLE);
3027	spin_unlock(lock: &journal->j_list_lock);
3028	schedule();
3029	finish_wait(wq_head: wq, wq_entry: &wait.wq_entry);
3030	goto restart;
3031	}
3032
3033	if (jinode->i_transaction) {
3034	list_del(entry: &jinode->i_list);
3035	jinode->i_transaction = NULL;
3036	}
3037	spin_unlock(lock: &journal->j_list_lock);
3038	}
3039
3040
3041	#ifdef CONFIG_PROC_FS
3042
3043	#define JBD2_STATS_PROC_NAME "fs/jbd2"
3044
3045	static void __init jbd2_create_jbd_stats_proc_entry(void)
3046	{
3047	proc_jbd2_stats = proc_mkdir(JBD2_STATS_PROC_NAME, NULL);
3048	}
3049
3050	static void __exit jbd2_remove_jbd_stats_proc_entry(void)
3051	{
3052	if (proc_jbd2_stats)
3053	remove_proc_entry(JBD2_STATS_PROC_NAME, NULL);
3054	}
3055
3056	#else
3057
3058	#define jbd2_create_jbd_stats_proc_entry() do {} while (0)
3059	#define jbd2_remove_jbd_stats_proc_entry() do {} while (0)
3060
3061	#endif
3062
3063	struct kmem_cache jbd2_handle_cache, jbd2_inode_cache;
3064
3065	static int __init jbd2_journal_init_inode_cache(void)
3066	{
3067	J_ASSERT(!jbd2_inode_cache);
3068	jbd2_inode_cache = KMEM_CACHE(jbd2_inode, `0`);
3069	if (!jbd2_inode_cache) {
3070	pr_emerg("JBD2: failed to create inode cache\n");
3071	return -ENOMEM;
3072	}
3073	return `0`;
3074	}
3075
3076	static int __init jbd2_journal_init_handle_cache(void)
3077	{
3078	J_ASSERT(!jbd2_handle_cache);
3079	jbd2_handle_cache = KMEM_CACHE(jbd2_journal_handle, SLAB_TEMPORARY);
3080	if (!jbd2_handle_cache) {
3081	printk(KERN_EMERG "JBD2: failed to create handle cache\n");
3082	return -ENOMEM;
3083	}
3084	return `0`;
3085	}
3086
3087	static void jbd2_journal_destroy_inode_cache(void)
3088	{
3089	kmem_cache_destroy(s: jbd2_inode_cache);
3090	jbd2_inode_cache = NULL;
3091	}
3092
3093	static void jbd2_journal_destroy_handle_cache(void)
3094	{
3095	kmem_cache_destroy(s: jbd2_handle_cache);
3096	jbd2_handle_cache = NULL;
3097	}
3098
3099	/*
3100	* Module startup and shutdown
3101	*/
3102
3103	static int __init journal_init_caches(void)
3104	{
3105	int ret;
3106
3107	ret = jbd2_journal_init_revoke_record_cache();
3108	if (ret == `0`)
3109	ret = jbd2_journal_init_revoke_table_cache();
3110	if (ret == `0`)
3111	ret = jbd2_journal_init_journal_head_cache();
3112	if (ret == `0`)
3113	ret = jbd2_journal_init_handle_cache();
3114	if (ret == `0`)
3115	ret = jbd2_journal_init_inode_cache();
3116	if (ret == `0`)
3117	ret = jbd2_journal_init_transaction_cache();
3118	return ret;
3119	}
3120
3121	static void jbd2_journal_destroy_caches(void)
3122	{
3123	jbd2_journal_destroy_revoke_record_cache();
3124	jbd2_journal_destroy_revoke_table_cache();
3125	jbd2_journal_destroy_journal_head_cache();
3126	jbd2_journal_destroy_handle_cache();
3127	jbd2_journal_destroy_inode_cache();
3128	jbd2_journal_destroy_transaction_cache();
3129	jbd2_journal_destroy_slabs();
3130	}
3131
3132	static int __init journal_init(void)
3133	{
3134	int ret;
3135
3136	BUILD_BUG_ON(sizeof(struct journal_superblock_s) != `1024`);
3137
3138	ret = journal_init_caches();
3139	if (ret == `0`) {
3140	jbd2_create_jbd_stats_proc_entry();
3141	} else {
3142	jbd2_journal_destroy_caches();
3143	}
3144	return ret;
3145	}
3146
3147	static void __exit journal_exit(void)
3148	{
3149	#ifdef CONFIG_JBD2_DEBUG
3150	int n = atomic_read(&nr_journal_heads);
3151	if (n)
3152	printk(KERN_ERR "JBD2: leaked %d journal_heads!\n", n);
3153	#endif
3154	jbd2_remove_jbd_stats_proc_entry();
3155	jbd2_journal_destroy_caches();
3156	}
3157
3158	MODULE_DESCRIPTION("Generic filesystem journal-writing module");
3159	MODULE_LICENSE("GPL");
3160	module_init(journal_init);
3161	module_exit(journal_exit);
3162
3163

Browse the source code of Linux/fs/jbd2/journal.c