1// SPDX-License-Identifier: GPL-2.0-only
2/* fs/fat/nfs.c
3 */
4
5#include <linux/exportfs.h>
6#include "fat.h"
7
8struct fat_fid {
9 u32 i_gen;
10 u32 i_pos_low;
11 u16 i_pos_hi;
12 u16 parent_i_pos_hi;
13 u32 parent_i_pos_low;
14 u32 parent_i_gen;
15};
16
17#define FAT_FID_SIZE_WITHOUT_PARENT 3
18#define FAT_FID_SIZE_WITH_PARENT (sizeof(struct fat_fid)/sizeof(u32))
19
20/*
21 * Look up a directory inode given its starting cluster.
22 */
23static struct inode *fat_dget(struct super_block *sb, int i_logstart)
24{
25 struct msdos_sb_info *sbi = MSDOS_SB(sb);
26 struct hlist_head *head;
27 struct msdos_inode_info *i;
28 struct inode *inode = NULL;
29
30 head = sbi->dir_hashtable + fat_dir_hash(logstart: i_logstart);
31 spin_lock(lock: &sbi->dir_hash_lock);
32 hlist_for_each_entry(i, head, i_dir_hash) {
33 BUG_ON(i->vfs_inode.i_sb != sb);
34 if (i->i_logstart != i_logstart)
35 continue;
36 inode = igrab(&i->vfs_inode);
37 if (inode)
38 break;
39 }
40 spin_unlock(lock: &sbi->dir_hash_lock);
41 return inode;
42}
43
44static struct inode *fat_ilookup(struct super_block *sb, u64 ino, loff_t i_pos)
45{
46 if (MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO)
47 return fat_iget(sb, i_pos);
48
49 else {
50 if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO))
51 return NULL;
52 return ilookup(sb, ino);
53 }
54}
55
56static struct inode *__fat_nfs_get_inode(struct super_block *sb,
57 u64 ino, u32 generation, loff_t i_pos)
58{
59 struct inode *inode = fat_ilookup(sb, ino, i_pos);
60
61 if (inode && generation && (inode->i_generation != generation)) {
62 iput(inode);
63 inode = NULL;
64 }
65 if (inode == NULL && MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
66 struct buffer_head *bh = NULL;
67 struct msdos_dir_entry *de ;
68 sector_t blocknr;
69 int offset;
70 fat_get_blknr_offset(sbi: MSDOS_SB(sb), i_pos, blknr: &blocknr, offset: &offset);
71 bh = sb_bread(sb, block: blocknr);
72 if (!bh) {
73 fat_msg(sb, KERN_ERR,
74 "unable to read block(%llu) for building NFS inode",
75 (llu)blocknr);
76 return inode;
77 }
78 de = (struct msdos_dir_entry *)bh->b_data;
79 /* If a file is deleted on server and client is not updated
80 * yet, we must not build the inode upon a lookup call.
81 */
82 if (IS_FREE(de[offset].name))
83 inode = NULL;
84 else
85 inode = fat_build_inode(sb, de: &de[offset], i_pos);
86 brelse(bh);
87 }
88
89 return inode;
90}
91
92static struct inode *fat_nfs_get_inode(struct super_block *sb,
93 u64 ino, u32 generation)
94{
95
96 return __fat_nfs_get_inode(sb, ino, generation, i_pos: 0);
97}
98
99static int
100fat_encode_fh_nostale(struct inode *inode, __u32 *fh, int *lenp,
101 struct inode *parent)
102{
103 int len = *lenp;
104 struct msdos_sb_info *sbi = MSDOS_SB(sb: inode->i_sb);
105 struct fat_fid *fid = (struct fat_fid *) fh;
106 loff_t i_pos;
107 int type = FILEID_FAT_WITHOUT_PARENT;
108
109 if (parent) {
110 if (len < FAT_FID_SIZE_WITH_PARENT) {
111 *lenp = FAT_FID_SIZE_WITH_PARENT;
112 return FILEID_INVALID;
113 }
114 } else {
115 if (len < FAT_FID_SIZE_WITHOUT_PARENT) {
116 *lenp = FAT_FID_SIZE_WITHOUT_PARENT;
117 return FILEID_INVALID;
118 }
119 }
120
121 i_pos = fat_i_pos_read(sbi, inode);
122 *lenp = FAT_FID_SIZE_WITHOUT_PARENT;
123 fid->i_gen = inode->i_generation;
124 fid->i_pos_low = i_pos & 0xFFFFFFFF;
125 fid->i_pos_hi = (i_pos >> 32) & 0xFFFF;
126 if (parent) {
127 i_pos = fat_i_pos_read(sbi, inode: parent);
128 fid->parent_i_pos_hi = (i_pos >> 32) & 0xFFFF;
129 fid->parent_i_pos_low = i_pos & 0xFFFFFFFF;
130 fid->parent_i_gen = parent->i_generation;
131 type = FILEID_FAT_WITH_PARENT;
132 *lenp = FAT_FID_SIZE_WITH_PARENT;
133 } else {
134 /*
135 * We need to initialize this field because the fh is actually
136 * 12 bytes long
137 */
138 fid->parent_i_pos_hi = 0;
139 }
140
141 return type;
142}
143
144/*
145 * Map a NFS file handle to a corresponding dentry.
146 * The dentry may or may not be connected to the filesystem root.
147 */
148static struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
149 int fh_len, int fh_type)
150{
151 return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
152 get_inode: fat_nfs_get_inode);
153}
154
155static struct dentry *fat_fh_to_dentry_nostale(struct super_block *sb,
156 struct fid *fh, int fh_len,
157 int fh_type)
158{
159 struct inode *inode = NULL;
160 struct fat_fid *fid = (struct fat_fid *)fh;
161 loff_t i_pos;
162
163 switch (fh_type) {
164 case FILEID_FAT_WITHOUT_PARENT:
165 if (fh_len < FAT_FID_SIZE_WITHOUT_PARENT)
166 return NULL;
167 break;
168 case FILEID_FAT_WITH_PARENT:
169 if (fh_len < FAT_FID_SIZE_WITH_PARENT)
170 return NULL;
171 break;
172 default:
173 return NULL;
174 }
175 i_pos = fid->i_pos_hi;
176 i_pos = (i_pos << 32) | (fid->i_pos_low);
177 inode = __fat_nfs_get_inode(sb, ino: 0, generation: fid->i_gen, i_pos);
178
179 return d_obtain_alias(inode);
180}
181
182/*
183 * Find the parent for a file specified by NFS handle.
184 * This requires that the handle contain the i_ino of the parent.
185 */
186static struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid,
187 int fh_len, int fh_type)
188{
189 return generic_fh_to_parent(sb, fid, fh_len, fh_type,
190 get_inode: fat_nfs_get_inode);
191}
192
193static struct dentry *fat_fh_to_parent_nostale(struct super_block *sb,
194 struct fid *fh, int fh_len,
195 int fh_type)
196{
197 struct inode *inode = NULL;
198 struct fat_fid *fid = (struct fat_fid *)fh;
199 loff_t i_pos;
200
201 if (fh_len < FAT_FID_SIZE_WITH_PARENT)
202 return NULL;
203
204 switch (fh_type) {
205 case FILEID_FAT_WITH_PARENT:
206 i_pos = fid->parent_i_pos_hi;
207 i_pos = (i_pos << 32) | (fid->parent_i_pos_low);
208 inode = __fat_nfs_get_inode(sb, ino: 0, generation: fid->parent_i_gen, i_pos);
209 break;
210 }
211
212 return d_obtain_alias(inode);
213}
214
215/*
216 * Rebuild the parent for a directory that is not connected
217 * to the filesystem root
218 */
219static
220struct inode *fat_rebuild_parent(struct super_block *sb, int parent_logstart)
221{
222 int search_clus, clus_to_match;
223 struct msdos_dir_entry *de;
224 struct inode *parent = NULL;
225 struct inode *dummy_grand_parent = NULL;
226 struct fat_slot_info sinfo;
227 struct msdos_sb_info *sbi = MSDOS_SB(sb);
228 sector_t blknr = fat_clus_to_blknr(sbi, clus: parent_logstart);
229 struct buffer_head *parent_bh = sb_bread(sb, block: blknr);
230 if (!parent_bh) {
231 fat_msg(sb, KERN_ERR,
232 "unable to read cluster of parent directory");
233 return NULL;
234 }
235
236 de = (struct msdos_dir_entry *) parent_bh->b_data;
237 clus_to_match = fat_get_start(sbi, de: &de[0]);
238 search_clus = fat_get_start(sbi, de: &de[1]);
239
240 dummy_grand_parent = fat_dget(sb, i_logstart: search_clus);
241 if (!dummy_grand_parent) {
242 dummy_grand_parent = new_inode(sb);
243 if (!dummy_grand_parent) {
244 brelse(bh: parent_bh);
245 return parent;
246 }
247
248 dummy_grand_parent->i_ino = iunique(sb, MSDOS_ROOT_INO);
249 fat_fill_inode(inode: dummy_grand_parent, de: &de[1]);
250 MSDOS_I(inode: dummy_grand_parent)->i_pos = -1;
251 }
252
253 if (!fat_scan_logstart(dir: dummy_grand_parent, i_logstart: clus_to_match, sinfo: &sinfo))
254 parent = fat_build_inode(sb, de: sinfo.de, i_pos: sinfo.i_pos);
255
256 brelse(bh: parent_bh);
257 iput(dummy_grand_parent);
258
259 return parent;
260}
261
262/*
263 * Find the parent for a directory that is not currently connected to
264 * the filesystem root.
265 *
266 * On entry, the caller holds d_inode(child_dir)->i_mutex.
267 */
268static struct dentry *fat_get_parent(struct dentry *child_dir)
269{
270 struct super_block *sb = child_dir->d_sb;
271 struct buffer_head *bh = NULL;
272 struct msdos_dir_entry *de;
273 struct inode *parent_inode = NULL;
274 struct msdos_sb_info *sbi = MSDOS_SB(sb);
275
276 if (!fat_get_dotdot_entry(dir: d_inode(dentry: child_dir), bh: &bh, de: &de)) {
277 int parent_logstart = fat_get_start(sbi, de);
278 parent_inode = fat_dget(sb, i_logstart: parent_logstart);
279 if (!parent_inode && sbi->options.nfs == FAT_NFS_NOSTALE_RO)
280 parent_inode = fat_rebuild_parent(sb, parent_logstart);
281 }
282 brelse(bh);
283
284 return d_obtain_alias(parent_inode);
285}
286
287const struct export_operations fat_export_ops = {
288 .encode_fh = generic_encode_ino32_fh,
289 .fh_to_dentry = fat_fh_to_dentry,
290 .fh_to_parent = fat_fh_to_parent,
291 .get_parent = fat_get_parent,
292};
293
294const struct export_operations fat_export_ops_nostale = {
295 .encode_fh = fat_encode_fh_nostale,
296 .fh_to_dentry = fat_fh_to_dentry_nostale,
297 .fh_to_parent = fat_fh_to_parent_nostale,
298 .get_parent = fat_get_parent,
299};
300