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 | |
8 | struct 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 | */ |
23 | static 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 | |
44 | static 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 | |
56 | static 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 | |
92 | static 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 | |
99 | static int |
100 | fat_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 | */ |
148 | static 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 | |
155 | static 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 | */ |
186 | static 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 | |
193 | static 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 | */ |
219 | static |
220 | struct 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 | */ |
268 | static 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 | |
287 | const 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 | |
294 | const 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 | |