SLUB slab validation: Move tracking information alloc outside of lock
[linux-2.6] / fs / ext4 / xattr.c
1 /*
2  * linux/fs/ext4/xattr.c
3  *
4  * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
5  *
6  * Fix by Harrison Xing <harrison@mountainviewdata.com>.
7  * Ext4 code with a lot of help from Eric Jarman <ejarman@acm.org>.
8  * Extended attributes for symlinks and special files added per
9  *  suggestion of Luka Renko <luka.renko@hermes.si>.
10  * xattr consolidation Copyright (c) 2004 James Morris <jmorris@redhat.com>,
11  *  Red Hat Inc.
12  * ea-in-inode support by Alex Tomas <alex@clusterfs.com> aka bzzz
13  *  and Andreas Gruenbacher <agruen@suse.de>.
14  */
15
16 /*
17  * Extended attributes are stored directly in inodes (on file systems with
18  * inodes bigger than 128 bytes) and on additional disk blocks. The i_file_acl
19  * field contains the block number if an inode uses an additional block. All
20  * attributes must fit in the inode and one additional block. Blocks that
21  * contain the identical set of attributes may be shared among several inodes.
22  * Identical blocks are detected by keeping a cache of blocks that have
23  * recently been accessed.
24  *
25  * The attributes in inodes and on blocks have a different header; the entries
26  * are stored in the same format:
27  *
28  *   +------------------+
29  *   | header           |
30  *   | entry 1          | |
31  *   | entry 2          | | growing downwards
32  *   | entry 3          | v
33  *   | four null bytes  |
34  *   | . . .            |
35  *   | value 1          | ^
36  *   | value 3          | | growing upwards
37  *   | value 2          | |
38  *   +------------------+
39  *
40  * The header is followed by multiple entry descriptors. In disk blocks, the
41  * entry descriptors are kept sorted. In inodes, they are unsorted. The
42  * attribute values are aligned to the end of the block in no specific order.
43  *
44  * Locking strategy
45  * ----------------
46  * EXT4_I(inode)->i_file_acl is protected by EXT4_I(inode)->xattr_sem.
47  * EA blocks are only changed if they are exclusive to an inode, so
48  * holding xattr_sem also means that nothing but the EA block's reference
49  * count can change. Multiple writers to the same block are synchronized
50  * by the buffer lock.
51  */
52
53 #include <linux/init.h>
54 #include <linux/fs.h>
55 #include <linux/slab.h>
56 #include <linux/ext4_jbd2.h>
57 #include <linux/ext4_fs.h>
58 #include <linux/mbcache.h>
59 #include <linux/quotaops.h>
60 #include <linux/rwsem.h>
61 #include "xattr.h"
62 #include "acl.h"
63
64 #define BHDR(bh) ((struct ext4_xattr_header *)((bh)->b_data))
65 #define ENTRY(ptr) ((struct ext4_xattr_entry *)(ptr))
66 #define BFIRST(bh) ENTRY(BHDR(bh)+1)
67 #define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
68
69 #define IHDR(inode, raw_inode) \
70         ((struct ext4_xattr_ibody_header *) \
71                 ((void *)raw_inode + \
72                  EXT4_GOOD_OLD_INODE_SIZE + \
73                  EXT4_I(inode)->i_extra_isize))
74 #define IFIRST(hdr) ((struct ext4_xattr_entry *)((hdr)+1))
75
76 #ifdef EXT4_XATTR_DEBUG
77 # define ea_idebug(inode, f...) do { \
78                 printk(KERN_DEBUG "inode %s:%lu: ", \
79                         inode->i_sb->s_id, inode->i_ino); \
80                 printk(f); \
81                 printk("\n"); \
82         } while (0)
83 # define ea_bdebug(bh, f...) do { \
84                 char b[BDEVNAME_SIZE]; \
85                 printk(KERN_DEBUG "block %s:%lu: ", \
86                         bdevname(bh->b_bdev, b), \
87                         (unsigned long) bh->b_blocknr); \
88                 printk(f); \
89                 printk("\n"); \
90         } while (0)
91 #else
92 # define ea_idebug(f...)
93 # define ea_bdebug(f...)
94 #endif
95
96 static void ext4_xattr_cache_insert(struct buffer_head *);
97 static struct buffer_head *ext4_xattr_cache_find(struct inode *,
98                                                  struct ext4_xattr_header *,
99                                                  struct mb_cache_entry **);
100 static void ext4_xattr_rehash(struct ext4_xattr_header *,
101                               struct ext4_xattr_entry *);
102
103 static struct mb_cache *ext4_xattr_cache;
104
105 static struct xattr_handler *ext4_xattr_handler_map[] = {
106         [EXT4_XATTR_INDEX_USER]              = &ext4_xattr_user_handler,
107 #ifdef CONFIG_EXT4DEV_FS_POSIX_ACL
108         [EXT4_XATTR_INDEX_POSIX_ACL_ACCESS]  = &ext4_xattr_acl_access_handler,
109         [EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT] = &ext4_xattr_acl_default_handler,
110 #endif
111         [EXT4_XATTR_INDEX_TRUSTED]           = &ext4_xattr_trusted_handler,
112 #ifdef CONFIG_EXT4DEV_FS_SECURITY
113         [EXT4_XATTR_INDEX_SECURITY]          = &ext4_xattr_security_handler,
114 #endif
115 };
116
117 struct xattr_handler *ext4_xattr_handlers[] = {
118         &ext4_xattr_user_handler,
119         &ext4_xattr_trusted_handler,
120 #ifdef CONFIG_EXT4DEV_FS_POSIX_ACL
121         &ext4_xattr_acl_access_handler,
122         &ext4_xattr_acl_default_handler,
123 #endif
124 #ifdef CONFIG_EXT4DEV_FS_SECURITY
125         &ext4_xattr_security_handler,
126 #endif
127         NULL
128 };
129
130 static inline struct xattr_handler *
131 ext4_xattr_handler(int name_index)
132 {
133         struct xattr_handler *handler = NULL;
134
135         if (name_index > 0 && name_index < ARRAY_SIZE(ext4_xattr_handler_map))
136                 handler = ext4_xattr_handler_map[name_index];
137         return handler;
138 }
139
140 /*
141  * Inode operation listxattr()
142  *
143  * dentry->d_inode->i_mutex: don't care
144  */
145 ssize_t
146 ext4_listxattr(struct dentry *dentry, char *buffer, size_t size)
147 {
148         return ext4_xattr_list(dentry->d_inode, buffer, size);
149 }
150
151 static int
152 ext4_xattr_check_names(struct ext4_xattr_entry *entry, void *end)
153 {
154         while (!IS_LAST_ENTRY(entry)) {
155                 struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(entry);
156                 if ((void *)next >= end)
157                         return -EIO;
158                 entry = next;
159         }
160         return 0;
161 }
162
163 static inline int
164 ext4_xattr_check_block(struct buffer_head *bh)
165 {
166         int error;
167
168         if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
169             BHDR(bh)->h_blocks != cpu_to_le32(1))
170                 return -EIO;
171         error = ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size);
172         return error;
173 }
174
175 static inline int
176 ext4_xattr_check_entry(struct ext4_xattr_entry *entry, size_t size)
177 {
178         size_t value_size = le32_to_cpu(entry->e_value_size);
179
180         if (entry->e_value_block != 0 || value_size > size ||
181             le16_to_cpu(entry->e_value_offs) + value_size > size)
182                 return -EIO;
183         return 0;
184 }
185
186 static int
187 ext4_xattr_find_entry(struct ext4_xattr_entry **pentry, int name_index,
188                       const char *name, size_t size, int sorted)
189 {
190         struct ext4_xattr_entry *entry;
191         size_t name_len;
192         int cmp = 1;
193
194         if (name == NULL)
195                 return -EINVAL;
196         name_len = strlen(name);
197         entry = *pentry;
198         for (; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
199                 cmp = name_index - entry->e_name_index;
200                 if (!cmp)
201                         cmp = name_len - entry->e_name_len;
202                 if (!cmp)
203                         cmp = memcmp(name, entry->e_name, name_len);
204                 if (cmp <= 0 && (sorted || cmp == 0))
205                         break;
206         }
207         *pentry = entry;
208         if (!cmp && ext4_xattr_check_entry(entry, size))
209                         return -EIO;
210         return cmp ? -ENODATA : 0;
211 }
212
213 static int
214 ext4_xattr_block_get(struct inode *inode, int name_index, const char *name,
215                      void *buffer, size_t buffer_size)
216 {
217         struct buffer_head *bh = NULL;
218         struct ext4_xattr_entry *entry;
219         size_t size;
220         int error;
221
222         ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
223                   name_index, name, buffer, (long)buffer_size);
224
225         error = -ENODATA;
226         if (!EXT4_I(inode)->i_file_acl)
227                 goto cleanup;
228         ea_idebug(inode, "reading block %u", EXT4_I(inode)->i_file_acl);
229         bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
230         if (!bh)
231                 goto cleanup;
232         ea_bdebug(bh, "b_count=%d, refcount=%d",
233                 atomic_read(&(bh->b_count)), le32_to_cpu(BHDR(bh)->h_refcount));
234         if (ext4_xattr_check_block(bh)) {
235 bad_block:      ext4_error(inode->i_sb, __FUNCTION__,
236                            "inode %lu: bad block %llu", inode->i_ino,
237                            EXT4_I(inode)->i_file_acl);
238                 error = -EIO;
239                 goto cleanup;
240         }
241         ext4_xattr_cache_insert(bh);
242         entry = BFIRST(bh);
243         error = ext4_xattr_find_entry(&entry, name_index, name, bh->b_size, 1);
244         if (error == -EIO)
245                 goto bad_block;
246         if (error)
247                 goto cleanup;
248         size = le32_to_cpu(entry->e_value_size);
249         if (buffer) {
250                 error = -ERANGE;
251                 if (size > buffer_size)
252                         goto cleanup;
253                 memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
254                        size);
255         }
256         error = size;
257
258 cleanup:
259         brelse(bh);
260         return error;
261 }
262
263 static int
264 ext4_xattr_ibody_get(struct inode *inode, int name_index, const char *name,
265                      void *buffer, size_t buffer_size)
266 {
267         struct ext4_xattr_ibody_header *header;
268         struct ext4_xattr_entry *entry;
269         struct ext4_inode *raw_inode;
270         struct ext4_iloc iloc;
271         size_t size;
272         void *end;
273         int error;
274
275         if (!(EXT4_I(inode)->i_state & EXT4_STATE_XATTR))
276                 return -ENODATA;
277         error = ext4_get_inode_loc(inode, &iloc);
278         if (error)
279                 return error;
280         raw_inode = ext4_raw_inode(&iloc);
281         header = IHDR(inode, raw_inode);
282         entry = IFIRST(header);
283         end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
284         error = ext4_xattr_check_names(entry, end);
285         if (error)
286                 goto cleanup;
287         error = ext4_xattr_find_entry(&entry, name_index, name,
288                                       end - (void *)entry, 0);
289         if (error)
290                 goto cleanup;
291         size = le32_to_cpu(entry->e_value_size);
292         if (buffer) {
293                 error = -ERANGE;
294                 if (size > buffer_size)
295                         goto cleanup;
296                 memcpy(buffer, (void *)IFIRST(header) +
297                        le16_to_cpu(entry->e_value_offs), size);
298         }
299         error = size;
300
301 cleanup:
302         brelse(iloc.bh);
303         return error;
304 }
305
306 /*
307  * ext4_xattr_get()
308  *
309  * Copy an extended attribute into the buffer
310  * provided, or compute the buffer size required.
311  * Buffer is NULL to compute the size of the buffer required.
312  *
313  * Returns a negative error number on failure, or the number of bytes
314  * used / required on success.
315  */
316 int
317 ext4_xattr_get(struct inode *inode, int name_index, const char *name,
318                void *buffer, size_t buffer_size)
319 {
320         int error;
321
322         down_read(&EXT4_I(inode)->xattr_sem);
323         error = ext4_xattr_ibody_get(inode, name_index, name, buffer,
324                                      buffer_size);
325         if (error == -ENODATA)
326                 error = ext4_xattr_block_get(inode, name_index, name, buffer,
327                                              buffer_size);
328         up_read(&EXT4_I(inode)->xattr_sem);
329         return error;
330 }
331
332 static int
333 ext4_xattr_list_entries(struct inode *inode, struct ext4_xattr_entry *entry,
334                         char *buffer, size_t buffer_size)
335 {
336         size_t rest = buffer_size;
337
338         for (; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
339                 struct xattr_handler *handler =
340                         ext4_xattr_handler(entry->e_name_index);
341
342                 if (handler) {
343                         size_t size = handler->list(inode, buffer, rest,
344                                                     entry->e_name,
345                                                     entry->e_name_len);
346                         if (buffer) {
347                                 if (size > rest)
348                                         return -ERANGE;
349                                 buffer += size;
350                         }
351                         rest -= size;
352                 }
353         }
354         return buffer_size - rest;
355 }
356
357 static int
358 ext4_xattr_block_list(struct inode *inode, char *buffer, size_t buffer_size)
359 {
360         struct buffer_head *bh = NULL;
361         int error;
362
363         ea_idebug(inode, "buffer=%p, buffer_size=%ld",
364                   buffer, (long)buffer_size);
365
366         error = 0;
367         if (!EXT4_I(inode)->i_file_acl)
368                 goto cleanup;
369         ea_idebug(inode, "reading block %u", EXT4_I(inode)->i_file_acl);
370         bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
371         error = -EIO;
372         if (!bh)
373                 goto cleanup;
374         ea_bdebug(bh, "b_count=%d, refcount=%d",
375                 atomic_read(&(bh->b_count)), le32_to_cpu(BHDR(bh)->h_refcount));
376         if (ext4_xattr_check_block(bh)) {
377                 ext4_error(inode->i_sb, __FUNCTION__,
378                            "inode %lu: bad block %llu", inode->i_ino,
379                            EXT4_I(inode)->i_file_acl);
380                 error = -EIO;
381                 goto cleanup;
382         }
383         ext4_xattr_cache_insert(bh);
384         error = ext4_xattr_list_entries(inode, BFIRST(bh), buffer, buffer_size);
385
386 cleanup:
387         brelse(bh);
388
389         return error;
390 }
391
392 static int
393 ext4_xattr_ibody_list(struct inode *inode, char *buffer, size_t buffer_size)
394 {
395         struct ext4_xattr_ibody_header *header;
396         struct ext4_inode *raw_inode;
397         struct ext4_iloc iloc;
398         void *end;
399         int error;
400
401         if (!(EXT4_I(inode)->i_state & EXT4_STATE_XATTR))
402                 return 0;
403         error = ext4_get_inode_loc(inode, &iloc);
404         if (error)
405                 return error;
406         raw_inode = ext4_raw_inode(&iloc);
407         header = IHDR(inode, raw_inode);
408         end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
409         error = ext4_xattr_check_names(IFIRST(header), end);
410         if (error)
411                 goto cleanup;
412         error = ext4_xattr_list_entries(inode, IFIRST(header),
413                                         buffer, buffer_size);
414
415 cleanup:
416         brelse(iloc.bh);
417         return error;
418 }
419
420 /*
421  * ext4_xattr_list()
422  *
423  * Copy a list of attribute names into the buffer
424  * provided, or compute the buffer size required.
425  * Buffer is NULL to compute the size of the buffer required.
426  *
427  * Returns a negative error number on failure, or the number of bytes
428  * used / required on success.
429  */
430 int
431 ext4_xattr_list(struct inode *inode, char *buffer, size_t buffer_size)
432 {
433         int i_error, b_error;
434
435         down_read(&EXT4_I(inode)->xattr_sem);
436         i_error = ext4_xattr_ibody_list(inode, buffer, buffer_size);
437         if (i_error < 0) {
438                 b_error = 0;
439         } else {
440                 if (buffer) {
441                         buffer += i_error;
442                         buffer_size -= i_error;
443                 }
444                 b_error = ext4_xattr_block_list(inode, buffer, buffer_size);
445                 if (b_error < 0)
446                         i_error = 0;
447         }
448         up_read(&EXT4_I(inode)->xattr_sem);
449         return i_error + b_error;
450 }
451
452 /*
453  * If the EXT4_FEATURE_COMPAT_EXT_ATTR feature of this file system is
454  * not set, set it.
455  */
456 static void ext4_xattr_update_super_block(handle_t *handle,
457                                           struct super_block *sb)
458 {
459         if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_EXT_ATTR))
460                 return;
461
462         if (ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh) == 0) {
463                 EXT4_SET_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_EXT_ATTR);
464                 sb->s_dirt = 1;
465                 ext4_journal_dirty_metadata(handle, EXT4_SB(sb)->s_sbh);
466         }
467 }
468
469 /*
470  * Release the xattr block BH: If the reference count is > 1, decrement
471  * it; otherwise free the block.
472  */
473 static void
474 ext4_xattr_release_block(handle_t *handle, struct inode *inode,
475                          struct buffer_head *bh)
476 {
477         struct mb_cache_entry *ce = NULL;
478         int error = 0;
479
480         ce = mb_cache_entry_get(ext4_xattr_cache, bh->b_bdev, bh->b_blocknr);
481         error = ext4_journal_get_write_access(handle, bh);
482         if (error)
483                 goto out;
484
485         lock_buffer(bh);
486         if (BHDR(bh)->h_refcount == cpu_to_le32(1)) {
487                 ea_bdebug(bh, "refcount now=0; freeing");
488                 if (ce)
489                         mb_cache_entry_free(ce);
490                 ext4_free_blocks(handle, inode, bh->b_blocknr, 1);
491                 get_bh(bh);
492                 ext4_forget(handle, 1, inode, bh, bh->b_blocknr);
493         } else {
494                 BHDR(bh)->h_refcount = cpu_to_le32(
495                                 le32_to_cpu(BHDR(bh)->h_refcount) - 1);
496                 error = ext4_journal_dirty_metadata(handle, bh);
497                 if (IS_SYNC(inode))
498                         handle->h_sync = 1;
499                 DQUOT_FREE_BLOCK(inode, 1);
500                 ea_bdebug(bh, "refcount now=%d; releasing",
501                           le32_to_cpu(BHDR(bh)->h_refcount));
502                 if (ce)
503                         mb_cache_entry_release(ce);
504         }
505         unlock_buffer(bh);
506 out:
507         ext4_std_error(inode->i_sb, error);
508         return;
509 }
510
511 struct ext4_xattr_info {
512         int name_index;
513         const char *name;
514         const void *value;
515         size_t value_len;
516 };
517
518 struct ext4_xattr_search {
519         struct ext4_xattr_entry *first;
520         void *base;
521         void *end;
522         struct ext4_xattr_entry *here;
523         int not_found;
524 };
525
526 static int
527 ext4_xattr_set_entry(struct ext4_xattr_info *i, struct ext4_xattr_search *s)
528 {
529         struct ext4_xattr_entry *last;
530         size_t free, min_offs = s->end - s->base, name_len = strlen(i->name);
531
532         /* Compute min_offs and last. */
533         last = s->first;
534         for (; !IS_LAST_ENTRY(last); last = EXT4_XATTR_NEXT(last)) {
535                 if (!last->e_value_block && last->e_value_size) {
536                         size_t offs = le16_to_cpu(last->e_value_offs);
537                         if (offs < min_offs)
538                                 min_offs = offs;
539                 }
540         }
541         free = min_offs - ((void *)last - s->base) - sizeof(__u32);
542         if (!s->not_found) {
543                 if (!s->here->e_value_block && s->here->e_value_size) {
544                         size_t size = le32_to_cpu(s->here->e_value_size);
545                         free += EXT4_XATTR_SIZE(size);
546                 }
547                 free += EXT4_XATTR_LEN(name_len);
548         }
549         if (i->value) {
550                 if (free < EXT4_XATTR_SIZE(i->value_len) ||
551                     free < EXT4_XATTR_LEN(name_len) +
552                            EXT4_XATTR_SIZE(i->value_len))
553                         return -ENOSPC;
554         }
555
556         if (i->value && s->not_found) {
557                 /* Insert the new name. */
558                 size_t size = EXT4_XATTR_LEN(name_len);
559                 size_t rest = (void *)last - (void *)s->here + sizeof(__u32);
560                 memmove((void *)s->here + size, s->here, rest);
561                 memset(s->here, 0, size);
562                 s->here->e_name_index = i->name_index;
563                 s->here->e_name_len = name_len;
564                 memcpy(s->here->e_name, i->name, name_len);
565         } else {
566                 if (!s->here->e_value_block && s->here->e_value_size) {
567                         void *first_val = s->base + min_offs;
568                         size_t offs = le16_to_cpu(s->here->e_value_offs);
569                         void *val = s->base + offs;
570                         size_t size = EXT4_XATTR_SIZE(
571                                 le32_to_cpu(s->here->e_value_size));
572
573                         if (i->value && size == EXT4_XATTR_SIZE(i->value_len)) {
574                                 /* The old and the new value have the same
575                                    size. Just replace. */
576                                 s->here->e_value_size =
577                                         cpu_to_le32(i->value_len);
578                                 memset(val + size - EXT4_XATTR_PAD, 0,
579                                        EXT4_XATTR_PAD); /* Clear pad bytes. */
580                                 memcpy(val, i->value, i->value_len);
581                                 return 0;
582                         }
583
584                         /* Remove the old value. */
585                         memmove(first_val + size, first_val, val - first_val);
586                         memset(first_val, 0, size);
587                         s->here->e_value_size = 0;
588                         s->here->e_value_offs = 0;
589                         min_offs += size;
590
591                         /* Adjust all value offsets. */
592                         last = s->first;
593                         while (!IS_LAST_ENTRY(last)) {
594                                 size_t o = le16_to_cpu(last->e_value_offs);
595                                 if (!last->e_value_block &&
596                                     last->e_value_size && o < offs)
597                                         last->e_value_offs =
598                                                 cpu_to_le16(o + size);
599                                 last = EXT4_XATTR_NEXT(last);
600                         }
601                 }
602                 if (!i->value) {
603                         /* Remove the old name. */
604                         size_t size = EXT4_XATTR_LEN(name_len);
605                         last = ENTRY((void *)last - size);
606                         memmove(s->here, (void *)s->here + size,
607                                 (void *)last - (void *)s->here + sizeof(__u32));
608                         memset(last, 0, size);
609                 }
610         }
611
612         if (i->value) {
613                 /* Insert the new value. */
614                 s->here->e_value_size = cpu_to_le32(i->value_len);
615                 if (i->value_len) {
616                         size_t size = EXT4_XATTR_SIZE(i->value_len);
617                         void *val = s->base + min_offs - size;
618                         s->here->e_value_offs = cpu_to_le16(min_offs - size);
619                         memset(val + size - EXT4_XATTR_PAD, 0,
620                                EXT4_XATTR_PAD); /* Clear the pad bytes. */
621                         memcpy(val, i->value, i->value_len);
622                 }
623         }
624         return 0;
625 }
626
627 struct ext4_xattr_block_find {
628         struct ext4_xattr_search s;
629         struct buffer_head *bh;
630 };
631
632 static int
633 ext4_xattr_block_find(struct inode *inode, struct ext4_xattr_info *i,
634                       struct ext4_xattr_block_find *bs)
635 {
636         struct super_block *sb = inode->i_sb;
637         int error;
638
639         ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
640                   i->name_index, i->name, i->value, (long)i->value_len);
641
642         if (EXT4_I(inode)->i_file_acl) {
643                 /* The inode already has an extended attribute block. */
644                 bs->bh = sb_bread(sb, EXT4_I(inode)->i_file_acl);
645                 error = -EIO;
646                 if (!bs->bh)
647                         goto cleanup;
648                 ea_bdebug(bs->bh, "b_count=%d, refcount=%d",
649                         atomic_read(&(bs->bh->b_count)),
650                         le32_to_cpu(BHDR(bs->bh)->h_refcount));
651                 if (ext4_xattr_check_block(bs->bh)) {
652                         ext4_error(sb, __FUNCTION__,
653                                 "inode %lu: bad block %llu", inode->i_ino,
654                                 EXT4_I(inode)->i_file_acl);
655                         error = -EIO;
656                         goto cleanup;
657                 }
658                 /* Find the named attribute. */
659                 bs->s.base = BHDR(bs->bh);
660                 bs->s.first = BFIRST(bs->bh);
661                 bs->s.end = bs->bh->b_data + bs->bh->b_size;
662                 bs->s.here = bs->s.first;
663                 error = ext4_xattr_find_entry(&bs->s.here, i->name_index,
664                                               i->name, bs->bh->b_size, 1);
665                 if (error && error != -ENODATA)
666                         goto cleanup;
667                 bs->s.not_found = error;
668         }
669         error = 0;
670
671 cleanup:
672         return error;
673 }
674
675 static int
676 ext4_xattr_block_set(handle_t *handle, struct inode *inode,
677                      struct ext4_xattr_info *i,
678                      struct ext4_xattr_block_find *bs)
679 {
680         struct super_block *sb = inode->i_sb;
681         struct buffer_head *new_bh = NULL;
682         struct ext4_xattr_search *s = &bs->s;
683         struct mb_cache_entry *ce = NULL;
684         int error = 0;
685
686 #define header(x) ((struct ext4_xattr_header *)(x))
687
688         if (i->value && i->value_len > sb->s_blocksize)
689                 return -ENOSPC;
690         if (s->base) {
691                 ce = mb_cache_entry_get(ext4_xattr_cache, bs->bh->b_bdev,
692                                         bs->bh->b_blocknr);
693                 error = ext4_journal_get_write_access(handle, bs->bh);
694                 if (error)
695                         goto cleanup;
696                 lock_buffer(bs->bh);
697
698                 if (header(s->base)->h_refcount == cpu_to_le32(1)) {
699                         if (ce) {
700                                 mb_cache_entry_free(ce);
701                                 ce = NULL;
702                         }
703                         ea_bdebug(bs->bh, "modifying in-place");
704                         error = ext4_xattr_set_entry(i, s);
705                         if (!error) {
706                                 if (!IS_LAST_ENTRY(s->first))
707                                         ext4_xattr_rehash(header(s->base),
708                                                           s->here);
709                                 ext4_xattr_cache_insert(bs->bh);
710                         }
711                         unlock_buffer(bs->bh);
712                         if (error == -EIO)
713                                 goto bad_block;
714                         if (!error)
715                                 error = ext4_journal_dirty_metadata(handle,
716                                                                     bs->bh);
717                         if (error)
718                                 goto cleanup;
719                         goto inserted;
720                 } else {
721                         int offset = (char *)s->here - bs->bh->b_data;
722
723                         unlock_buffer(bs->bh);
724                         jbd2_journal_release_buffer(handle, bs->bh);
725                         if (ce) {
726                                 mb_cache_entry_release(ce);
727                                 ce = NULL;
728                         }
729                         ea_bdebug(bs->bh, "cloning");
730                         s->base = kmalloc(bs->bh->b_size, GFP_KERNEL);
731                         error = -ENOMEM;
732                         if (s->base == NULL)
733                                 goto cleanup;
734                         memcpy(s->base, BHDR(bs->bh), bs->bh->b_size);
735                         s->first = ENTRY(header(s->base)+1);
736                         header(s->base)->h_refcount = cpu_to_le32(1);
737                         s->here = ENTRY(s->base + offset);
738                         s->end = s->base + bs->bh->b_size;
739                 }
740         } else {
741                 /* Allocate a buffer where we construct the new block. */
742                 s->base = kmalloc(sb->s_blocksize, GFP_KERNEL);
743                 /* assert(header == s->base) */
744                 error = -ENOMEM;
745                 if (s->base == NULL)
746                         goto cleanup;
747                 memset(s->base, 0, sb->s_blocksize);
748                 header(s->base)->h_magic = cpu_to_le32(EXT4_XATTR_MAGIC);
749                 header(s->base)->h_blocks = cpu_to_le32(1);
750                 header(s->base)->h_refcount = cpu_to_le32(1);
751                 s->first = ENTRY(header(s->base)+1);
752                 s->here = ENTRY(header(s->base)+1);
753                 s->end = s->base + sb->s_blocksize;
754         }
755
756         error = ext4_xattr_set_entry(i, s);
757         if (error == -EIO)
758                 goto bad_block;
759         if (error)
760                 goto cleanup;
761         if (!IS_LAST_ENTRY(s->first))
762                 ext4_xattr_rehash(header(s->base), s->here);
763
764 inserted:
765         if (!IS_LAST_ENTRY(s->first)) {
766                 new_bh = ext4_xattr_cache_find(inode, header(s->base), &ce);
767                 if (new_bh) {
768                         /* We found an identical block in the cache. */
769                         if (new_bh == bs->bh)
770                                 ea_bdebug(new_bh, "keeping");
771                         else {
772                                 /* The old block is released after updating
773                                    the inode. */
774                                 error = -EDQUOT;
775                                 if (DQUOT_ALLOC_BLOCK(inode, 1))
776                                         goto cleanup;
777                                 error = ext4_journal_get_write_access(handle,
778                                                                       new_bh);
779                                 if (error)
780                                         goto cleanup_dquot;
781                                 lock_buffer(new_bh);
782                                 BHDR(new_bh)->h_refcount = cpu_to_le32(1 +
783                                         le32_to_cpu(BHDR(new_bh)->h_refcount));
784                                 ea_bdebug(new_bh, "reusing; refcount now=%d",
785                                         le32_to_cpu(BHDR(new_bh)->h_refcount));
786                                 unlock_buffer(new_bh);
787                                 error = ext4_journal_dirty_metadata(handle,
788                                                                     new_bh);
789                                 if (error)
790                                         goto cleanup_dquot;
791                         }
792                         mb_cache_entry_release(ce);
793                         ce = NULL;
794                 } else if (bs->bh && s->base == bs->bh->b_data) {
795                         /* We were modifying this block in-place. */
796                         ea_bdebug(bs->bh, "keeping this block");
797                         new_bh = bs->bh;
798                         get_bh(new_bh);
799                 } else {
800                         /* We need to allocate a new block */
801                         ext4_fsblk_t goal = le32_to_cpu(
802                                         EXT4_SB(sb)->s_es->s_first_data_block) +
803                                 (ext4_fsblk_t)EXT4_I(inode)->i_block_group *
804                                 EXT4_BLOCKS_PER_GROUP(sb);
805                         ext4_fsblk_t block = ext4_new_block(handle, inode,
806                                                         goal, &error);
807                         if (error)
808                                 goto cleanup;
809                         ea_idebug(inode, "creating block %d", block);
810
811                         new_bh = sb_getblk(sb, block);
812                         if (!new_bh) {
813 getblk_failed:
814                                 ext4_free_blocks(handle, inode, block, 1);
815                                 error = -EIO;
816                                 goto cleanup;
817                         }
818                         lock_buffer(new_bh);
819                         error = ext4_journal_get_create_access(handle, new_bh);
820                         if (error) {
821                                 unlock_buffer(new_bh);
822                                 goto getblk_failed;
823                         }
824                         memcpy(new_bh->b_data, s->base, new_bh->b_size);
825                         set_buffer_uptodate(new_bh);
826                         unlock_buffer(new_bh);
827                         ext4_xattr_cache_insert(new_bh);
828                         error = ext4_journal_dirty_metadata(handle, new_bh);
829                         if (error)
830                                 goto cleanup;
831                 }
832         }
833
834         /* Update the inode. */
835         EXT4_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
836
837         /* Drop the previous xattr block. */
838         if (bs->bh && bs->bh != new_bh)
839                 ext4_xattr_release_block(handle, inode, bs->bh);
840         error = 0;
841
842 cleanup:
843         if (ce)
844                 mb_cache_entry_release(ce);
845         brelse(new_bh);
846         if (!(bs->bh && s->base == bs->bh->b_data))
847                 kfree(s->base);
848
849         return error;
850
851 cleanup_dquot:
852         DQUOT_FREE_BLOCK(inode, 1);
853         goto cleanup;
854
855 bad_block:
856         ext4_error(inode->i_sb, __FUNCTION__,
857                    "inode %lu: bad block %llu", inode->i_ino,
858                    EXT4_I(inode)->i_file_acl);
859         goto cleanup;
860
861 #undef header
862 }
863
864 struct ext4_xattr_ibody_find {
865         struct ext4_xattr_search s;
866         struct ext4_iloc iloc;
867 };
868
869 static int
870 ext4_xattr_ibody_find(struct inode *inode, struct ext4_xattr_info *i,
871                       struct ext4_xattr_ibody_find *is)
872 {
873         struct ext4_xattr_ibody_header *header;
874         struct ext4_inode *raw_inode;
875         int error;
876
877         if (EXT4_I(inode)->i_extra_isize == 0)
878                 return 0;
879         raw_inode = ext4_raw_inode(&is->iloc);
880         header = IHDR(inode, raw_inode);
881         is->s.base = is->s.first = IFIRST(header);
882         is->s.here = is->s.first;
883         is->s.end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
884         if (EXT4_I(inode)->i_state & EXT4_STATE_XATTR) {
885                 error = ext4_xattr_check_names(IFIRST(header), is->s.end);
886                 if (error)
887                         return error;
888                 /* Find the named attribute. */
889                 error = ext4_xattr_find_entry(&is->s.here, i->name_index,
890                                               i->name, is->s.end -
891                                               (void *)is->s.base, 0);
892                 if (error && error != -ENODATA)
893                         return error;
894                 is->s.not_found = error;
895         }
896         return 0;
897 }
898
899 static int
900 ext4_xattr_ibody_set(handle_t *handle, struct inode *inode,
901                      struct ext4_xattr_info *i,
902                      struct ext4_xattr_ibody_find *is)
903 {
904         struct ext4_xattr_ibody_header *header;
905         struct ext4_xattr_search *s = &is->s;
906         int error;
907
908         if (EXT4_I(inode)->i_extra_isize == 0)
909                 return -ENOSPC;
910         error = ext4_xattr_set_entry(i, s);
911         if (error)
912                 return error;
913         header = IHDR(inode, ext4_raw_inode(&is->iloc));
914         if (!IS_LAST_ENTRY(s->first)) {
915                 header->h_magic = cpu_to_le32(EXT4_XATTR_MAGIC);
916                 EXT4_I(inode)->i_state |= EXT4_STATE_XATTR;
917         } else {
918                 header->h_magic = cpu_to_le32(0);
919                 EXT4_I(inode)->i_state &= ~EXT4_STATE_XATTR;
920         }
921         return 0;
922 }
923
924 /*
925  * ext4_xattr_set_handle()
926  *
927  * Create, replace or remove an extended attribute for this inode. Buffer
928  * is NULL to remove an existing extended attribute, and non-NULL to
929  * either replace an existing extended attribute, or create a new extended
930  * attribute. The flags XATTR_REPLACE and XATTR_CREATE
931  * specify that an extended attribute must exist and must not exist
932  * previous to the call, respectively.
933  *
934  * Returns 0, or a negative error number on failure.
935  */
936 int
937 ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
938                       const char *name, const void *value, size_t value_len,
939                       int flags)
940 {
941         struct ext4_xattr_info i = {
942                 .name_index = name_index,
943                 .name = name,
944                 .value = value,
945                 .value_len = value_len,
946
947         };
948         struct ext4_xattr_ibody_find is = {
949                 .s = { .not_found = -ENODATA, },
950         };
951         struct ext4_xattr_block_find bs = {
952                 .s = { .not_found = -ENODATA, },
953         };
954         int error;
955
956         if (!name)
957                 return -EINVAL;
958         if (strlen(name) > 255)
959                 return -ERANGE;
960         down_write(&EXT4_I(inode)->xattr_sem);
961         error = ext4_get_inode_loc(inode, &is.iloc);
962         if (error)
963                 goto cleanup;
964
965         if (EXT4_I(inode)->i_state & EXT4_STATE_NEW) {
966                 struct ext4_inode *raw_inode = ext4_raw_inode(&is.iloc);
967                 memset(raw_inode, 0, EXT4_SB(inode->i_sb)->s_inode_size);
968                 EXT4_I(inode)->i_state &= ~EXT4_STATE_NEW;
969         }
970
971         error = ext4_xattr_ibody_find(inode, &i, &is);
972         if (error)
973                 goto cleanup;
974         if (is.s.not_found)
975                 error = ext4_xattr_block_find(inode, &i, &bs);
976         if (error)
977                 goto cleanup;
978         if (is.s.not_found && bs.s.not_found) {
979                 error = -ENODATA;
980                 if (flags & XATTR_REPLACE)
981                         goto cleanup;
982                 error = 0;
983                 if (!value)
984                         goto cleanup;
985         } else {
986                 error = -EEXIST;
987                 if (flags & XATTR_CREATE)
988                         goto cleanup;
989         }
990         error = ext4_journal_get_write_access(handle, is.iloc.bh);
991         if (error)
992                 goto cleanup;
993         if (!value) {
994                 if (!is.s.not_found)
995                         error = ext4_xattr_ibody_set(handle, inode, &i, &is);
996                 else if (!bs.s.not_found)
997                         error = ext4_xattr_block_set(handle, inode, &i, &bs);
998         } else {
999                 error = ext4_xattr_ibody_set(handle, inode, &i, &is);
1000                 if (!error && !bs.s.not_found) {
1001                         i.value = NULL;
1002                         error = ext4_xattr_block_set(handle, inode, &i, &bs);
1003                 } else if (error == -ENOSPC) {
1004                         error = ext4_xattr_block_set(handle, inode, &i, &bs);
1005                         if (error)
1006                                 goto cleanup;
1007                         if (!is.s.not_found) {
1008                                 i.value = NULL;
1009                                 error = ext4_xattr_ibody_set(handle, inode, &i,
1010                                                              &is);
1011                         }
1012                 }
1013         }
1014         if (!error) {
1015                 ext4_xattr_update_super_block(handle, inode->i_sb);
1016                 inode->i_ctime = CURRENT_TIME_SEC;
1017                 error = ext4_mark_iloc_dirty(handle, inode, &is.iloc);
1018                 /*
1019                  * The bh is consumed by ext4_mark_iloc_dirty, even with
1020                  * error != 0.
1021                  */
1022                 is.iloc.bh = NULL;
1023                 if (IS_SYNC(inode))
1024                         handle->h_sync = 1;
1025         }
1026
1027 cleanup:
1028         brelse(is.iloc.bh);
1029         brelse(bs.bh);
1030         up_write(&EXT4_I(inode)->xattr_sem);
1031         return error;
1032 }
1033
1034 /*
1035  * ext4_xattr_set()
1036  *
1037  * Like ext4_xattr_set_handle, but start from an inode. This extended
1038  * attribute modification is a filesystem transaction by itself.
1039  *
1040  * Returns 0, or a negative error number on failure.
1041  */
1042 int
1043 ext4_xattr_set(struct inode *inode, int name_index, const char *name,
1044                const void *value, size_t value_len, int flags)
1045 {
1046         handle_t *handle;
1047         int error, retries = 0;
1048
1049 retry:
1050         handle = ext4_journal_start(inode, EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
1051         if (IS_ERR(handle)) {
1052                 error = PTR_ERR(handle);
1053         } else {
1054                 int error2;
1055
1056                 error = ext4_xattr_set_handle(handle, inode, name_index, name,
1057                                               value, value_len, flags);
1058                 error2 = ext4_journal_stop(handle);
1059                 if (error == -ENOSPC &&
1060                     ext4_should_retry_alloc(inode->i_sb, &retries))
1061                         goto retry;
1062                 if (error == 0)
1063                         error = error2;
1064         }
1065
1066         return error;
1067 }
1068
1069 /*
1070  * ext4_xattr_delete_inode()
1071  *
1072  * Free extended attribute resources associated with this inode. This
1073  * is called immediately before an inode is freed. We have exclusive
1074  * access to the inode.
1075  */
1076 void
1077 ext4_xattr_delete_inode(handle_t *handle, struct inode *inode)
1078 {
1079         struct buffer_head *bh = NULL;
1080
1081         if (!EXT4_I(inode)->i_file_acl)
1082                 goto cleanup;
1083         bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
1084         if (!bh) {
1085                 ext4_error(inode->i_sb, __FUNCTION__,
1086                         "inode %lu: block %llu read error", inode->i_ino,
1087                         EXT4_I(inode)->i_file_acl);
1088                 goto cleanup;
1089         }
1090         if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
1091             BHDR(bh)->h_blocks != cpu_to_le32(1)) {
1092                 ext4_error(inode->i_sb, __FUNCTION__,
1093                         "inode %lu: bad block %llu", inode->i_ino,
1094                         EXT4_I(inode)->i_file_acl);
1095                 goto cleanup;
1096         }
1097         ext4_xattr_release_block(handle, inode, bh);
1098         EXT4_I(inode)->i_file_acl = 0;
1099
1100 cleanup:
1101         brelse(bh);
1102 }
1103
1104 /*
1105  * ext4_xattr_put_super()
1106  *
1107  * This is called when a file system is unmounted.
1108  */
1109 void
1110 ext4_xattr_put_super(struct super_block *sb)
1111 {
1112         mb_cache_shrink(sb->s_bdev);
1113 }
1114
1115 /*
1116  * ext4_xattr_cache_insert()
1117  *
1118  * Create a new entry in the extended attribute cache, and insert
1119  * it unless such an entry is already in the cache.
1120  *
1121  * Returns 0, or a negative error number on failure.
1122  */
1123 static void
1124 ext4_xattr_cache_insert(struct buffer_head *bh)
1125 {
1126         __u32 hash = le32_to_cpu(BHDR(bh)->h_hash);
1127         struct mb_cache_entry *ce;
1128         int error;
1129
1130         ce = mb_cache_entry_alloc(ext4_xattr_cache);
1131         if (!ce) {
1132                 ea_bdebug(bh, "out of memory");
1133                 return;
1134         }
1135         error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, &hash);
1136         if (error) {
1137                 mb_cache_entry_free(ce);
1138                 if (error == -EBUSY) {
1139                         ea_bdebug(bh, "already in cache");
1140                         error = 0;
1141                 }
1142         } else {
1143                 ea_bdebug(bh, "inserting [%x]", (int)hash);
1144                 mb_cache_entry_release(ce);
1145         }
1146 }
1147
1148 /*
1149  * ext4_xattr_cmp()
1150  *
1151  * Compare two extended attribute blocks for equality.
1152  *
1153  * Returns 0 if the blocks are equal, 1 if they differ, and
1154  * a negative error number on errors.
1155  */
1156 static int
1157 ext4_xattr_cmp(struct ext4_xattr_header *header1,
1158                struct ext4_xattr_header *header2)
1159 {
1160         struct ext4_xattr_entry *entry1, *entry2;
1161
1162         entry1 = ENTRY(header1+1);
1163         entry2 = ENTRY(header2+1);
1164         while (!IS_LAST_ENTRY(entry1)) {
1165                 if (IS_LAST_ENTRY(entry2))
1166                         return 1;
1167                 if (entry1->e_hash != entry2->e_hash ||
1168                     entry1->e_name_index != entry2->e_name_index ||
1169                     entry1->e_name_len != entry2->e_name_len ||
1170                     entry1->e_value_size != entry2->e_value_size ||
1171                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
1172                         return 1;
1173                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
1174                         return -EIO;
1175                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
1176                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
1177                            le32_to_cpu(entry1->e_value_size)))
1178                         return 1;
1179
1180                 entry1 = EXT4_XATTR_NEXT(entry1);
1181                 entry2 = EXT4_XATTR_NEXT(entry2);
1182         }
1183         if (!IS_LAST_ENTRY(entry2))
1184                 return 1;
1185         return 0;
1186 }
1187
1188 /*
1189  * ext4_xattr_cache_find()
1190  *
1191  * Find an identical extended attribute block.
1192  *
1193  * Returns a pointer to the block found, or NULL if such a block was
1194  * not found or an error occurred.
1195  */
1196 static struct buffer_head *
1197 ext4_xattr_cache_find(struct inode *inode, struct ext4_xattr_header *header,
1198                       struct mb_cache_entry **pce)
1199 {
1200         __u32 hash = le32_to_cpu(header->h_hash);
1201         struct mb_cache_entry *ce;
1202
1203         if (!header->h_hash)
1204                 return NULL;  /* never share */
1205         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
1206 again:
1207         ce = mb_cache_entry_find_first(ext4_xattr_cache, 0,
1208                                        inode->i_sb->s_bdev, hash);
1209         while (ce) {
1210                 struct buffer_head *bh;
1211
1212                 if (IS_ERR(ce)) {
1213                         if (PTR_ERR(ce) == -EAGAIN)
1214                                 goto again;
1215                         break;
1216                 }
1217                 bh = sb_bread(inode->i_sb, ce->e_block);
1218                 if (!bh) {
1219                         ext4_error(inode->i_sb, __FUNCTION__,
1220                                 "inode %lu: block %lu read error",
1221                                 inode->i_ino, (unsigned long) ce->e_block);
1222                 } else if (le32_to_cpu(BHDR(bh)->h_refcount) >=
1223                                 EXT4_XATTR_REFCOUNT_MAX) {
1224                         ea_idebug(inode, "block %lu refcount %d>=%d",
1225                                   (unsigned long) ce->e_block,
1226                                   le32_to_cpu(BHDR(bh)->h_refcount),
1227                                           EXT4_XATTR_REFCOUNT_MAX);
1228                 } else if (ext4_xattr_cmp(header, BHDR(bh)) == 0) {
1229                         *pce = ce;
1230                         return bh;
1231                 }
1232                 brelse(bh);
1233                 ce = mb_cache_entry_find_next(ce, 0, inode->i_sb->s_bdev, hash);
1234         }
1235         return NULL;
1236 }
1237
1238 #define NAME_HASH_SHIFT 5
1239 #define VALUE_HASH_SHIFT 16
1240
1241 /*
1242  * ext4_xattr_hash_entry()
1243  *
1244  * Compute the hash of an extended attribute.
1245  */
1246 static inline void ext4_xattr_hash_entry(struct ext4_xattr_header *header,
1247                                          struct ext4_xattr_entry *entry)
1248 {
1249         __u32 hash = 0;
1250         char *name = entry->e_name;
1251         int n;
1252
1253         for (n=0; n < entry->e_name_len; n++) {
1254                 hash = (hash << NAME_HASH_SHIFT) ^
1255                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
1256                        *name++;
1257         }
1258
1259         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
1260                 __le32 *value = (__le32 *)((char *)header +
1261                         le16_to_cpu(entry->e_value_offs));
1262                 for (n = (le32_to_cpu(entry->e_value_size) +
1263                      EXT4_XATTR_ROUND) >> EXT4_XATTR_PAD_BITS; n; n--) {
1264                         hash = (hash << VALUE_HASH_SHIFT) ^
1265                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
1266                                le32_to_cpu(*value++);
1267                 }
1268         }
1269         entry->e_hash = cpu_to_le32(hash);
1270 }
1271
1272 #undef NAME_HASH_SHIFT
1273 #undef VALUE_HASH_SHIFT
1274
1275 #define BLOCK_HASH_SHIFT 16
1276
1277 /*
1278  * ext4_xattr_rehash()
1279  *
1280  * Re-compute the extended attribute hash value after an entry has changed.
1281  */
1282 static void ext4_xattr_rehash(struct ext4_xattr_header *header,
1283                               struct ext4_xattr_entry *entry)
1284 {
1285         struct ext4_xattr_entry *here;
1286         __u32 hash = 0;
1287
1288         ext4_xattr_hash_entry(header, entry);
1289         here = ENTRY(header+1);
1290         while (!IS_LAST_ENTRY(here)) {
1291                 if (!here->e_hash) {
1292                         /* Block is not shared if an entry's hash value == 0 */
1293                         hash = 0;
1294                         break;
1295                 }
1296                 hash = (hash << BLOCK_HASH_SHIFT) ^
1297                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1298                        le32_to_cpu(here->e_hash);
1299                 here = EXT4_XATTR_NEXT(here);
1300         }
1301         header->h_hash = cpu_to_le32(hash);
1302 }
1303
1304 #undef BLOCK_HASH_SHIFT
1305
1306 int __init
1307 init_ext4_xattr(void)
1308 {
1309         ext4_xattr_cache = mb_cache_create("ext4_xattr", NULL,
1310                 sizeof(struct mb_cache_entry) +
1311                 sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]), 1, 6);
1312         if (!ext4_xattr_cache)
1313                 return -ENOMEM;
1314         return 0;
1315 }
1316
1317 void
1318 exit_ext4_xattr(void)
1319 {
1320         if (ext4_xattr_cache)
1321                 mb_cache_destroy(ext4_xattr_cache);
1322         ext4_xattr_cache = NULL;
1323 }