Merge ssh://master.kernel.org/pub/scm/linux/kernel/git/sam/kbuild
[linux-2.6] / fs / ext2 / xattr.c
1 /*
2  * linux/fs/ext2/xattr.c
3  *
4  * Copyright (C) 2001-2003 Andreas Gruenbacher <agruen@suse.de>
5  *
6  * Fix by Harrison Xing <harrison@mountainviewdata.com>.
7  * Extended attributes for symlinks and special files added per
8  *  suggestion of Luka Renko <luka.renko@hermes.si>.
9  * xattr consolidation Copyright (c) 2004 James Morris <jmorris@redhat.com>,
10  *  Red Hat Inc.
11  *
12  */
13
14 /*
15  * Extended attributes are stored on disk blocks allocated outside of
16  * any inode. The i_file_acl field is then made to point to this allocated
17  * block. If all extended attributes of an inode are identical, these
18  * inodes may share the same extended attribute block. Such situations
19  * are automatically detected by keeping a cache of recent attribute block
20  * numbers and hashes over the block's contents in memory.
21  *
22  *
23  * Extended attribute block layout:
24  *
25  *   +------------------+
26  *   | header           |
27  *   | entry 1          | |
28  *   | entry 2          | | growing downwards
29  *   | entry 3          | v
30  *   | four null bytes  |
31  *   | . . .            |
32  *   | value 1          | ^
33  *   | value 3          | | growing upwards
34  *   | value 2          | |
35  *   +------------------+
36  *
37  * The block header is followed by multiple entry descriptors. These entry
38  * descriptors are variable in size, and alligned to EXT2_XATTR_PAD
39  * byte boundaries. The entry descriptors are sorted by attribute name,
40  * so that two extended attribute blocks can be compared efficiently.
41  *
42  * Attribute values are aligned to the end of the block, stored in
43  * no specific order. They are also padded to EXT2_XATTR_PAD byte
44  * boundaries. No additional gaps are left between them.
45  *
46  * Locking strategy
47  * ----------------
48  * EXT2_I(inode)->i_file_acl is protected by EXT2_I(inode)->xattr_sem.
49  * EA blocks are only changed if they are exclusive to an inode, so
50  * holding xattr_sem also means that nothing but the EA block's reference
51  * count will change. Multiple writers to an EA block are synchronized
52  * by the bh lock. No more than a single bh lock is held at any time
53  * to avoid deadlocks.
54  */
55
56 #include <linux/buffer_head.h>
57 #include <linux/module.h>
58 #include <linux/init.h>
59 #include <linux/slab.h>
60 #include <linux/mbcache.h>
61 #include <linux/quotaops.h>
62 #include <linux/rwsem.h>
63 #include "ext2.h"
64 #include "xattr.h"
65 #include "acl.h"
66
67 #define HDR(bh) ((struct ext2_xattr_header *)((bh)->b_data))
68 #define ENTRY(ptr) ((struct ext2_xattr_entry *)(ptr))
69 #define FIRST_ENTRY(bh) ENTRY(HDR(bh)+1)
70 #define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
71
72 #ifdef EXT2_XATTR_DEBUG
73 # define ea_idebug(inode, f...) do { \
74                 printk(KERN_DEBUG "inode %s:%ld: ", \
75                         inode->i_sb->s_id, inode->i_ino); \
76                 printk(f); \
77                 printk("\n"); \
78         } while (0)
79 # define ea_bdebug(bh, f...) do { \
80                 char b[BDEVNAME_SIZE]; \
81                 printk(KERN_DEBUG "block %s:%lu: ", \
82                         bdevname(bh->b_bdev, b), \
83                         (unsigned long) bh->b_blocknr); \
84                 printk(f); \
85                 printk("\n"); \
86         } while (0)
87 #else
88 # define ea_idebug(f...)
89 # define ea_bdebug(f...)
90 #endif
91
92 static int ext2_xattr_set2(struct inode *, struct buffer_head *,
93                            struct ext2_xattr_header *);
94
95 static int ext2_xattr_cache_insert(struct buffer_head *);
96 static struct buffer_head *ext2_xattr_cache_find(struct inode *,
97                                                  struct ext2_xattr_header *);
98 static void ext2_xattr_rehash(struct ext2_xattr_header *,
99                               struct ext2_xattr_entry *);
100
101 static struct mb_cache *ext2_xattr_cache;
102
103 static struct xattr_handler *ext2_xattr_handler_map[] = {
104         [EXT2_XATTR_INDEX_USER]              = &ext2_xattr_user_handler,
105 #ifdef CONFIG_EXT2_FS_POSIX_ACL
106         [EXT2_XATTR_INDEX_POSIX_ACL_ACCESS]  = &ext2_xattr_acl_access_handler,
107         [EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &ext2_xattr_acl_default_handler,
108 #endif
109         [EXT2_XATTR_INDEX_TRUSTED]           = &ext2_xattr_trusted_handler,
110 #ifdef CONFIG_EXT2_FS_SECURITY
111         [EXT2_XATTR_INDEX_SECURITY]          = &ext2_xattr_security_handler,
112 #endif
113 };
114
115 struct xattr_handler *ext2_xattr_handlers[] = {
116         &ext2_xattr_user_handler,
117         &ext2_xattr_trusted_handler,
118 #ifdef CONFIG_EXT2_FS_POSIX_ACL
119         &ext2_xattr_acl_access_handler,
120         &ext2_xattr_acl_default_handler,
121 #endif
122 #ifdef CONFIG_EXT2_FS_SECURITY
123         &ext2_xattr_security_handler,
124 #endif
125         NULL
126 };
127
128 static inline struct xattr_handler *
129 ext2_xattr_handler(int name_index)
130 {
131         struct xattr_handler *handler = NULL;
132
133         if (name_index > 0 && name_index < ARRAY_SIZE(ext2_xattr_handler_map))
134                 handler = ext2_xattr_handler_map[name_index];
135         return handler;
136 }
137
138 /*
139  * ext2_xattr_get()
140  *
141  * Copy an extended attribute into the buffer
142  * provided, or compute the buffer size required.
143  * Buffer is NULL to compute the size of the buffer required.
144  *
145  * Returns a negative error number on failure, or the number of bytes
146  * used / required on success.
147  */
148 int
149 ext2_xattr_get(struct inode *inode, int name_index, const char *name,
150                void *buffer, size_t buffer_size)
151 {
152         struct buffer_head *bh = NULL;
153         struct ext2_xattr_entry *entry;
154         size_t name_len, size;
155         char *end;
156         int error;
157
158         ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
159                   name_index, name, buffer, (long)buffer_size);
160
161         if (name == NULL)
162                 return -EINVAL;
163         down_read(&EXT2_I(inode)->xattr_sem);
164         error = -ENODATA;
165         if (!EXT2_I(inode)->i_file_acl)
166                 goto cleanup;
167         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
168         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
169         error = -EIO;
170         if (!bh)
171                 goto cleanup;
172         ea_bdebug(bh, "b_count=%d, refcount=%d",
173                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
174         end = bh->b_data + bh->b_size;
175         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
176             HDR(bh)->h_blocks != cpu_to_le32(1)) {
177 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_get",
178                         "inode %ld: bad block %d", inode->i_ino,
179                         EXT2_I(inode)->i_file_acl);
180                 error = -EIO;
181                 goto cleanup;
182         }
183         /* find named attribute */
184         name_len = strlen(name);
185
186         error = -ERANGE;
187         if (name_len > 255)
188                 goto cleanup;
189         entry = FIRST_ENTRY(bh);
190         while (!IS_LAST_ENTRY(entry)) {
191                 struct ext2_xattr_entry *next =
192                         EXT2_XATTR_NEXT(entry);
193                 if ((char *)next >= end)
194                         goto bad_block;
195                 if (name_index == entry->e_name_index &&
196                     name_len == entry->e_name_len &&
197                     memcmp(name, entry->e_name, name_len) == 0)
198                         goto found;
199                 entry = next;
200         }
201         /* Check the remaining name entries */
202         while (!IS_LAST_ENTRY(entry)) {
203                 struct ext2_xattr_entry *next =
204                         EXT2_XATTR_NEXT(entry);
205                 if ((char *)next >= end)
206                         goto bad_block;
207                 entry = next;
208         }
209         if (ext2_xattr_cache_insert(bh))
210                 ea_idebug(inode, "cache insert failed");
211         error = -ENODATA;
212         goto cleanup;
213 found:
214         /* check the buffer size */
215         if (entry->e_value_block != 0)
216                 goto bad_block;
217         size = le32_to_cpu(entry->e_value_size);
218         if (size > inode->i_sb->s_blocksize ||
219             le16_to_cpu(entry->e_value_offs) + size > inode->i_sb->s_blocksize)
220                 goto bad_block;
221
222         if (ext2_xattr_cache_insert(bh))
223                 ea_idebug(inode, "cache insert failed");
224         if (buffer) {
225                 error = -ERANGE;
226                 if (size > buffer_size)
227                         goto cleanup;
228                 /* return value of attribute */
229                 memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
230                         size);
231         }
232         error = size;
233
234 cleanup:
235         brelse(bh);
236         up_read(&EXT2_I(inode)->xattr_sem);
237
238         return error;
239 }
240
241 /*
242  * ext2_xattr_list()
243  *
244  * Copy a list of attribute names into the buffer
245  * provided, or compute the buffer size required.
246  * Buffer is NULL to compute the size of the buffer required.
247  *
248  * Returns a negative error number on failure, or the number of bytes
249  * used / required on success.
250  */
251 static int
252 ext2_xattr_list(struct inode *inode, char *buffer, size_t buffer_size)
253 {
254         struct buffer_head *bh = NULL;
255         struct ext2_xattr_entry *entry;
256         char *end;
257         size_t rest = buffer_size;
258         int error;
259
260         ea_idebug(inode, "buffer=%p, buffer_size=%ld",
261                   buffer, (long)buffer_size);
262
263         down_read(&EXT2_I(inode)->xattr_sem);
264         error = 0;
265         if (!EXT2_I(inode)->i_file_acl)
266                 goto cleanup;
267         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
268         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
269         error = -EIO;
270         if (!bh)
271                 goto cleanup;
272         ea_bdebug(bh, "b_count=%d, refcount=%d",
273                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
274         end = bh->b_data + bh->b_size;
275         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
276             HDR(bh)->h_blocks != cpu_to_le32(1)) {
277 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_list",
278                         "inode %ld: bad block %d", inode->i_ino,
279                         EXT2_I(inode)->i_file_acl);
280                 error = -EIO;
281                 goto cleanup;
282         }
283
284         /* check the on-disk data structure */
285         entry = FIRST_ENTRY(bh);
286         while (!IS_LAST_ENTRY(entry)) {
287                 struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(entry);
288
289                 if ((char *)next >= end)
290                         goto bad_block;
291                 entry = next;
292         }
293         if (ext2_xattr_cache_insert(bh))
294                 ea_idebug(inode, "cache insert failed");
295
296         /* list the attribute names */
297         for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
298              entry = EXT2_XATTR_NEXT(entry)) {
299                 struct xattr_handler *handler =
300                         ext2_xattr_handler(entry->e_name_index);
301
302                 if (handler) {
303                         size_t size = handler->list(inode, buffer, rest,
304                                                     entry->e_name,
305                                                     entry->e_name_len);
306                         if (buffer) {
307                                 if (size > rest) {
308                                         error = -ERANGE;
309                                         goto cleanup;
310                                 }
311                                 buffer += size;
312                         }
313                         rest -= size;
314                 }
315         }
316         error = buffer_size - rest;  /* total size */
317
318 cleanup:
319         brelse(bh);
320         up_read(&EXT2_I(inode)->xattr_sem);
321
322         return error;
323 }
324
325 /*
326  * Inode operation listxattr()
327  *
328  * dentry->d_inode->i_mutex: don't care
329  */
330 ssize_t
331 ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
332 {
333         return ext2_xattr_list(dentry->d_inode, buffer, size);
334 }
335
336 /*
337  * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
338  * not set, set it.
339  */
340 static void ext2_xattr_update_super_block(struct super_block *sb)
341 {
342         if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
343                 return;
344
345         lock_super(sb);
346         EXT2_SB(sb)->s_es->s_feature_compat |=
347                 cpu_to_le32(EXT2_FEATURE_COMPAT_EXT_ATTR);
348         sb->s_dirt = 1;
349         mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
350         unlock_super(sb);
351 }
352
353 /*
354  * ext2_xattr_set()
355  *
356  * Create, replace or remove an extended attribute for this inode. Buffer
357  * is NULL to remove an existing extended attribute, and non-NULL to
358  * either replace an existing extended attribute, or create a new extended
359  * attribute. The flags XATTR_REPLACE and XATTR_CREATE
360  * specify that an extended attribute must exist and must not exist
361  * previous to the call, respectively.
362  *
363  * Returns 0, or a negative error number on failure.
364  */
365 int
366 ext2_xattr_set(struct inode *inode, int name_index, const char *name,
367                const void *value, size_t value_len, int flags)
368 {
369         struct super_block *sb = inode->i_sb;
370         struct buffer_head *bh = NULL;
371         struct ext2_xattr_header *header = NULL;
372         struct ext2_xattr_entry *here, *last;
373         size_t name_len, free, min_offs = sb->s_blocksize;
374         int not_found = 1, error;
375         char *end;
376         
377         /*
378          * header -- Points either into bh, or to a temporarily
379          *           allocated buffer.
380          * here -- The named entry found, or the place for inserting, within
381          *         the block pointed to by header.
382          * last -- Points right after the last named entry within the block
383          *         pointed to by header.
384          * min_offs -- The offset of the first value (values are aligned
385          *             towards the end of the block).
386          * end -- Points right after the block pointed to by header.
387          */
388         
389         ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
390                   name_index, name, value, (long)value_len);
391
392         if (value == NULL)
393                 value_len = 0;
394         if (name == NULL)
395                 return -EINVAL;
396         name_len = strlen(name);
397         if (name_len > 255 || value_len > sb->s_blocksize)
398                 return -ERANGE;
399         down_write(&EXT2_I(inode)->xattr_sem);
400         if (EXT2_I(inode)->i_file_acl) {
401                 /* The inode already has an extended attribute block. */
402                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
403                 error = -EIO;
404                 if (!bh)
405                         goto cleanup;
406                 ea_bdebug(bh, "b_count=%d, refcount=%d",
407                         atomic_read(&(bh->b_count)),
408                         le32_to_cpu(HDR(bh)->h_refcount));
409                 header = HDR(bh);
410                 end = bh->b_data + bh->b_size;
411                 if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
412                     header->h_blocks != cpu_to_le32(1)) {
413 bad_block:              ext2_error(sb, "ext2_xattr_set",
414                                 "inode %ld: bad block %d", inode->i_ino, 
415                                    EXT2_I(inode)->i_file_acl);
416                         error = -EIO;
417                         goto cleanup;
418                 }
419                 /* Find the named attribute. */
420                 here = FIRST_ENTRY(bh);
421                 while (!IS_LAST_ENTRY(here)) {
422                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
423                         if ((char *)next >= end)
424                                 goto bad_block;
425                         if (!here->e_value_block && here->e_value_size) {
426                                 size_t offs = le16_to_cpu(here->e_value_offs);
427                                 if (offs < min_offs)
428                                         min_offs = offs;
429                         }
430                         not_found = name_index - here->e_name_index;
431                         if (!not_found)
432                                 not_found = name_len - here->e_name_len;
433                         if (!not_found)
434                                 not_found = memcmp(name, here->e_name,name_len);
435                         if (not_found <= 0)
436                                 break;
437                         here = next;
438                 }
439                 last = here;
440                 /* We still need to compute min_offs and last. */
441                 while (!IS_LAST_ENTRY(last)) {
442                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
443                         if ((char *)next >= end)
444                                 goto bad_block;
445                         if (!last->e_value_block && last->e_value_size) {
446                                 size_t offs = le16_to_cpu(last->e_value_offs);
447                                 if (offs < min_offs)
448                                         min_offs = offs;
449                         }
450                         last = next;
451                 }
452
453                 /* Check whether we have enough space left. */
454                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
455         } else {
456                 /* We will use a new extended attribute block. */
457                 free = sb->s_blocksize -
458                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
459                 here = last = NULL;  /* avoid gcc uninitialized warning. */
460         }
461
462         if (not_found) {
463                 /* Request to remove a nonexistent attribute? */
464                 error = -ENODATA;
465                 if (flags & XATTR_REPLACE)
466                         goto cleanup;
467                 error = 0;
468                 if (value == NULL)
469                         goto cleanup;
470         } else {
471                 /* Request to create an existing attribute? */
472                 error = -EEXIST;
473                 if (flags & XATTR_CREATE)
474                         goto cleanup;
475                 if (!here->e_value_block && here->e_value_size) {
476                         size_t size = le32_to_cpu(here->e_value_size);
477
478                         if (le16_to_cpu(here->e_value_offs) + size > 
479                             sb->s_blocksize || size > sb->s_blocksize)
480                                 goto bad_block;
481                         free += EXT2_XATTR_SIZE(size);
482                 }
483                 free += EXT2_XATTR_LEN(name_len);
484         }
485         error = -ENOSPC;
486         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
487                 goto cleanup;
488
489         /* Here we know that we can set the new attribute. */
490
491         if (header) {
492                 struct mb_cache_entry *ce;
493
494                 /* assert(header == HDR(bh)); */
495                 ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev,
496                                         bh->b_blocknr);
497                 lock_buffer(bh);
498                 if (header->h_refcount == cpu_to_le32(1)) {
499                         ea_bdebug(bh, "modifying in-place");
500                         if (ce)
501                                 mb_cache_entry_free(ce);
502                         /* keep the buffer locked while modifying it. */
503                 } else {
504                         int offset;
505
506                         if (ce)
507                                 mb_cache_entry_release(ce);
508                         unlock_buffer(bh);
509                         ea_bdebug(bh, "cloning");
510                         header = kmalloc(bh->b_size, GFP_KERNEL);
511                         error = -ENOMEM;
512                         if (header == NULL)
513                                 goto cleanup;
514                         memcpy(header, HDR(bh), bh->b_size);
515                         header->h_refcount = cpu_to_le32(1);
516
517                         offset = (char *)here - bh->b_data;
518                         here = ENTRY((char *)header + offset);
519                         offset = (char *)last - bh->b_data;
520                         last = ENTRY((char *)header + offset);
521                 }
522         } else {
523                 /* Allocate a buffer where we construct the new block. */
524                 header = kmalloc(sb->s_blocksize, GFP_KERNEL);
525                 error = -ENOMEM;
526                 if (header == NULL)
527                         goto cleanup;
528                 memset(header, 0, sb->s_blocksize);
529                 end = (char *)header + sb->s_blocksize;
530                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
531                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
532                 last = here = ENTRY(header+1);
533         }
534
535         /* Iff we are modifying the block in-place, bh is locked here. */
536
537         if (not_found) {
538                 /* Insert the new name. */
539                 size_t size = EXT2_XATTR_LEN(name_len);
540                 size_t rest = (char *)last - (char *)here;
541                 memmove((char *)here + size, here, rest);
542                 memset(here, 0, size);
543                 here->e_name_index = name_index;
544                 here->e_name_len = name_len;
545                 memcpy(here->e_name, name, name_len);
546         } else {
547                 if (!here->e_value_block && here->e_value_size) {
548                         char *first_val = (char *)header + min_offs;
549                         size_t offs = le16_to_cpu(here->e_value_offs);
550                         char *val = (char *)header + offs;
551                         size_t size = EXT2_XATTR_SIZE(
552                                 le32_to_cpu(here->e_value_size));
553
554                         if (size == EXT2_XATTR_SIZE(value_len)) {
555                                 /* The old and the new value have the same
556                                    size. Just replace. */
557                                 here->e_value_size = cpu_to_le32(value_len);
558                                 memset(val + size - EXT2_XATTR_PAD, 0,
559                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
560                                 memcpy(val, value, value_len);
561                                 goto skip_replace;
562                         }
563
564                         /* Remove the old value. */
565                         memmove(first_val + size, first_val, val - first_val);
566                         memset(first_val, 0, size);
567                         here->e_value_offs = 0;
568                         min_offs += size;
569
570                         /* Adjust all value offsets. */
571                         last = ENTRY(header+1);
572                         while (!IS_LAST_ENTRY(last)) {
573                                 size_t o = le16_to_cpu(last->e_value_offs);
574                                 if (!last->e_value_block && o < offs)
575                                         last->e_value_offs =
576                                                 cpu_to_le16(o + size);
577                                 last = EXT2_XATTR_NEXT(last);
578                         }
579                 }
580                 if (value == NULL) {
581                         /* Remove the old name. */
582                         size_t size = EXT2_XATTR_LEN(name_len);
583                         last = ENTRY((char *)last - size);
584                         memmove(here, (char*)here + size,
585                                 (char*)last - (char*)here);
586                         memset(last, 0, size);
587                 }
588         }
589
590         if (value != NULL) {
591                 /* Insert the new value. */
592                 here->e_value_size = cpu_to_le32(value_len);
593                 if (value_len) {
594                         size_t size = EXT2_XATTR_SIZE(value_len);
595                         char *val = (char *)header + min_offs - size;
596                         here->e_value_offs =
597                                 cpu_to_le16((char *)val - (char *)header);
598                         memset(val + size - EXT2_XATTR_PAD, 0,
599                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
600                         memcpy(val, value, value_len);
601                 }
602         }
603
604 skip_replace:
605         if (IS_LAST_ENTRY(ENTRY(header+1))) {
606                 /* This block is now empty. */
607                 if (bh && header == HDR(bh))
608                         unlock_buffer(bh);  /* we were modifying in-place. */
609                 error = ext2_xattr_set2(inode, bh, NULL);
610         } else {
611                 ext2_xattr_rehash(header, here);
612                 if (bh && header == HDR(bh))
613                         unlock_buffer(bh);  /* we were modifying in-place. */
614                 error = ext2_xattr_set2(inode, bh, header);
615         }
616
617 cleanup:
618         brelse(bh);
619         if (!(bh && header == HDR(bh)))
620                 kfree(header);
621         up_write(&EXT2_I(inode)->xattr_sem);
622
623         return error;
624 }
625
626 /*
627  * Second half of ext2_xattr_set(): Update the file system.
628  */
629 static int
630 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
631                 struct ext2_xattr_header *header)
632 {
633         struct super_block *sb = inode->i_sb;
634         struct buffer_head *new_bh = NULL;
635         int error;
636
637         if (header) {
638                 new_bh = ext2_xattr_cache_find(inode, header);
639                 if (new_bh) {
640                         /* We found an identical block in the cache. */
641                         if (new_bh == old_bh) {
642                                 ea_bdebug(new_bh, "keeping this block");
643                         } else {
644                                 /* The old block is released after updating
645                                    the inode.  */
646                                 ea_bdebug(new_bh, "reusing block");
647
648                                 error = -EDQUOT;
649                                 if (DQUOT_ALLOC_BLOCK(inode, 1)) {
650                                         unlock_buffer(new_bh);
651                                         goto cleanup;
652                                 }
653                                 HDR(new_bh)->h_refcount = cpu_to_le32(1 +
654                                         le32_to_cpu(HDR(new_bh)->h_refcount));
655                                 ea_bdebug(new_bh, "refcount now=%d",
656                                         le32_to_cpu(HDR(new_bh)->h_refcount));
657                         }
658                         unlock_buffer(new_bh);
659                 } else if (old_bh && header == HDR(old_bh)) {
660                         /* Keep this block. No need to lock the block as we
661                            don't need to change the reference count. */
662                         new_bh = old_bh;
663                         get_bh(new_bh);
664                         ext2_xattr_cache_insert(new_bh);
665                 } else {
666                         /* We need to allocate a new block */
667                         int goal = le32_to_cpu(EXT2_SB(sb)->s_es->
668                                                            s_first_data_block) +
669                                    EXT2_I(inode)->i_block_group *
670                                    EXT2_BLOCKS_PER_GROUP(sb);
671                         int block = ext2_new_block(inode, goal,
672                                                    NULL, NULL, &error);
673                         if (error)
674                                 goto cleanup;
675                         ea_idebug(inode, "creating block %d", block);
676
677                         new_bh = sb_getblk(sb, block);
678                         if (!new_bh) {
679                                 ext2_free_blocks(inode, block, 1);
680                                 error = -EIO;
681                                 goto cleanup;
682                         }
683                         lock_buffer(new_bh);
684                         memcpy(new_bh->b_data, header, new_bh->b_size);
685                         set_buffer_uptodate(new_bh);
686                         unlock_buffer(new_bh);
687                         ext2_xattr_cache_insert(new_bh);
688                         
689                         ext2_xattr_update_super_block(sb);
690                 }
691                 mark_buffer_dirty(new_bh);
692                 if (IS_SYNC(inode)) {
693                         sync_dirty_buffer(new_bh);
694                         error = -EIO;
695                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
696                                 goto cleanup;
697                 }
698         }
699
700         /* Update the inode. */
701         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
702         inode->i_ctime = CURRENT_TIME_SEC;
703         if (IS_SYNC(inode)) {
704                 error = ext2_sync_inode (inode);
705                 /* In case sync failed due to ENOSPC the inode was actually
706                  * written (only some dirty data were not) so we just proceed
707                  * as if nothing happened and cleanup the unused block */
708                 if (error && error != -ENOSPC) {
709                         if (new_bh && new_bh != old_bh)
710                                 DQUOT_FREE_BLOCK(inode, 1);
711                         goto cleanup;
712                 }
713         } else
714                 mark_inode_dirty(inode);
715
716         error = 0;
717         if (old_bh && old_bh != new_bh) {
718                 struct mb_cache_entry *ce;
719
720                 /*
721                  * If there was an old block and we are no longer using it,
722                  * release the old block.
723                  */
724                 ce = mb_cache_entry_get(ext2_xattr_cache, old_bh->b_bdev,
725                                         old_bh->b_blocknr);
726                 lock_buffer(old_bh);
727                 if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
728                         /* Free the old block. */
729                         if (ce)
730                                 mb_cache_entry_free(ce);
731                         ea_bdebug(old_bh, "freeing");
732                         ext2_free_blocks(inode, old_bh->b_blocknr, 1);
733                         /* We let our caller release old_bh, so we
734                          * need to duplicate the buffer before. */
735                         get_bh(old_bh);
736                         bforget(old_bh);
737                 } else {
738                         /* Decrement the refcount only. */
739                         HDR(old_bh)->h_refcount = cpu_to_le32(
740                                 le32_to_cpu(HDR(old_bh)->h_refcount) - 1);
741                         if (ce)
742                                 mb_cache_entry_release(ce);
743                         DQUOT_FREE_BLOCK(inode, 1);
744                         mark_buffer_dirty(old_bh);
745                         ea_bdebug(old_bh, "refcount now=%d",
746                                 le32_to_cpu(HDR(old_bh)->h_refcount));
747                 }
748                 unlock_buffer(old_bh);
749         }
750
751 cleanup:
752         brelse(new_bh);
753
754         return error;
755 }
756
757 /*
758  * ext2_xattr_delete_inode()
759  *
760  * Free extended attribute resources associated with this inode. This
761  * is called immediately before an inode is freed.
762  */
763 void
764 ext2_xattr_delete_inode(struct inode *inode)
765 {
766         struct buffer_head *bh = NULL;
767         struct mb_cache_entry *ce;
768
769         down_write(&EXT2_I(inode)->xattr_sem);
770         if (!EXT2_I(inode)->i_file_acl)
771                 goto cleanup;
772         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
773         if (!bh) {
774                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
775                         "inode %ld: block %d read error", inode->i_ino,
776                         EXT2_I(inode)->i_file_acl);
777                 goto cleanup;
778         }
779         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
780         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
781             HDR(bh)->h_blocks != cpu_to_le32(1)) {
782                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
783                         "inode %ld: bad block %d", inode->i_ino,
784                         EXT2_I(inode)->i_file_acl);
785                 goto cleanup;
786         }
787         ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev, bh->b_blocknr);
788         lock_buffer(bh);
789         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
790                 if (ce)
791                         mb_cache_entry_free(ce);
792                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
793                 get_bh(bh);
794                 bforget(bh);
795         } else {
796                 HDR(bh)->h_refcount = cpu_to_le32(
797                         le32_to_cpu(HDR(bh)->h_refcount) - 1);
798                 if (ce)
799                         mb_cache_entry_release(ce);
800                 mark_buffer_dirty(bh);
801                 if (IS_SYNC(inode))
802                         sync_dirty_buffer(bh);
803                 DQUOT_FREE_BLOCK(inode, 1);
804         }
805         ea_bdebug(bh, "refcount now=%d", le32_to_cpu(HDR(bh)->h_refcount) - 1);
806         unlock_buffer(bh);
807         EXT2_I(inode)->i_file_acl = 0;
808
809 cleanup:
810         brelse(bh);
811         up_write(&EXT2_I(inode)->xattr_sem);
812 }
813
814 /*
815  * ext2_xattr_put_super()
816  *
817  * This is called when a file system is unmounted.
818  */
819 void
820 ext2_xattr_put_super(struct super_block *sb)
821 {
822         mb_cache_shrink(sb->s_bdev);
823 }
824
825
826 /*
827  * ext2_xattr_cache_insert()
828  *
829  * Create a new entry in the extended attribute cache, and insert
830  * it unless such an entry is already in the cache.
831  *
832  * Returns 0, or a negative error number on failure.
833  */
834 static int
835 ext2_xattr_cache_insert(struct buffer_head *bh)
836 {
837         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
838         struct mb_cache_entry *ce;
839         int error;
840
841         ce = mb_cache_entry_alloc(ext2_xattr_cache);
842         if (!ce)
843                 return -ENOMEM;
844         error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, &hash);
845         if (error) {
846                 mb_cache_entry_free(ce);
847                 if (error == -EBUSY) {
848                         ea_bdebug(bh, "already in cache (%d cache entries)",
849                                 atomic_read(&ext2_xattr_cache->c_entry_count));
850                         error = 0;
851                 }
852         } else {
853                 ea_bdebug(bh, "inserting [%x] (%d cache entries)", (int)hash,
854                           atomic_read(&ext2_xattr_cache->c_entry_count));
855                 mb_cache_entry_release(ce);
856         }
857         return error;
858 }
859
860 /*
861  * ext2_xattr_cmp()
862  *
863  * Compare two extended attribute blocks for equality.
864  *
865  * Returns 0 if the blocks are equal, 1 if they differ, and
866  * a negative error number on errors.
867  */
868 static int
869 ext2_xattr_cmp(struct ext2_xattr_header *header1,
870                struct ext2_xattr_header *header2)
871 {
872         struct ext2_xattr_entry *entry1, *entry2;
873
874         entry1 = ENTRY(header1+1);
875         entry2 = ENTRY(header2+1);
876         while (!IS_LAST_ENTRY(entry1)) {
877                 if (IS_LAST_ENTRY(entry2))
878                         return 1;
879                 if (entry1->e_hash != entry2->e_hash ||
880                     entry1->e_name_index != entry2->e_name_index ||
881                     entry1->e_name_len != entry2->e_name_len ||
882                     entry1->e_value_size != entry2->e_value_size ||
883                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
884                         return 1;
885                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
886                         return -EIO;
887                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
888                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
889                            le32_to_cpu(entry1->e_value_size)))
890                         return 1;
891
892                 entry1 = EXT2_XATTR_NEXT(entry1);
893                 entry2 = EXT2_XATTR_NEXT(entry2);
894         }
895         if (!IS_LAST_ENTRY(entry2))
896                 return 1;
897         return 0;
898 }
899
900 /*
901  * ext2_xattr_cache_find()
902  *
903  * Find an identical extended attribute block.
904  *
905  * Returns a locked buffer head to the block found, or NULL if such
906  * a block was not found or an error occurred.
907  */
908 static struct buffer_head *
909 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
910 {
911         __u32 hash = le32_to_cpu(header->h_hash);
912         struct mb_cache_entry *ce;
913
914         if (!header->h_hash)
915                 return NULL;  /* never share */
916         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
917 again:
918         ce = mb_cache_entry_find_first(ext2_xattr_cache, 0,
919                                        inode->i_sb->s_bdev, hash);
920         while (ce) {
921                 struct buffer_head *bh;
922
923                 if (IS_ERR(ce)) {
924                         if (PTR_ERR(ce) == -EAGAIN)
925                                 goto again;
926                         break;
927                 }
928
929                 bh = sb_bread(inode->i_sb, ce->e_block);
930                 if (!bh) {
931                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
932                                 "inode %ld: block %ld read error",
933                                 inode->i_ino, (unsigned long) ce->e_block);
934                 } else {
935                         lock_buffer(bh);
936                         if (le32_to_cpu(HDR(bh)->h_refcount) >
937                                    EXT2_XATTR_REFCOUNT_MAX) {
938                                 ea_idebug(inode, "block %ld refcount %d>%d",
939                                           (unsigned long) ce->e_block,
940                                           le32_to_cpu(HDR(bh)->h_refcount),
941                                           EXT2_XATTR_REFCOUNT_MAX);
942                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
943                                 ea_bdebug(bh, "b_count=%d",
944                                           atomic_read(&(bh->b_count)));
945                                 mb_cache_entry_release(ce);
946                                 return bh;
947                         }
948                         unlock_buffer(bh);
949                         brelse(bh);
950                 }
951                 ce = mb_cache_entry_find_next(ce, 0, inode->i_sb->s_bdev, hash);
952         }
953         return NULL;
954 }
955
956 #define NAME_HASH_SHIFT 5
957 #define VALUE_HASH_SHIFT 16
958
959 /*
960  * ext2_xattr_hash_entry()
961  *
962  * Compute the hash of an extended attribute.
963  */
964 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
965                                          struct ext2_xattr_entry *entry)
966 {
967         __u32 hash = 0;
968         char *name = entry->e_name;
969         int n;
970
971         for (n=0; n < entry->e_name_len; n++) {
972                 hash = (hash << NAME_HASH_SHIFT) ^
973                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
974                        *name++;
975         }
976
977         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
978                 __le32 *value = (__le32 *)((char *)header +
979                         le16_to_cpu(entry->e_value_offs));
980                 for (n = (le32_to_cpu(entry->e_value_size) +
981                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
982                         hash = (hash << VALUE_HASH_SHIFT) ^
983                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
984                                le32_to_cpu(*value++);
985                 }
986         }
987         entry->e_hash = cpu_to_le32(hash);
988 }
989
990 #undef NAME_HASH_SHIFT
991 #undef VALUE_HASH_SHIFT
992
993 #define BLOCK_HASH_SHIFT 16
994
995 /*
996  * ext2_xattr_rehash()
997  *
998  * Re-compute the extended attribute hash value after an entry has changed.
999  */
1000 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
1001                               struct ext2_xattr_entry *entry)
1002 {
1003         struct ext2_xattr_entry *here;
1004         __u32 hash = 0;
1005         
1006         ext2_xattr_hash_entry(header, entry);
1007         here = ENTRY(header+1);
1008         while (!IS_LAST_ENTRY(here)) {
1009                 if (!here->e_hash) {
1010                         /* Block is not shared if an entry's hash value == 0 */
1011                         hash = 0;
1012                         break;
1013                 }
1014                 hash = (hash << BLOCK_HASH_SHIFT) ^
1015                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1016                        le32_to_cpu(here->e_hash);
1017                 here = EXT2_XATTR_NEXT(here);
1018         }
1019         header->h_hash = cpu_to_le32(hash);
1020 }
1021
1022 #undef BLOCK_HASH_SHIFT
1023
1024 int __init
1025 init_ext2_xattr(void)
1026 {
1027         ext2_xattr_cache = mb_cache_create("ext2_xattr", NULL,
1028                 sizeof(struct mb_cache_entry) +
1029                 sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]), 1, 6);
1030         if (!ext2_xattr_cache)
1031                 return -ENOMEM;
1032         return 0;
1033 }
1034
1035 void
1036 exit_ext2_xattr(void)
1037 {
1038         mb_cache_destroy(ext2_xattr_cache);
1039 }