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[linux-3.10.git] / 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 aligned 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/init.h>
58 #include <linux/slab.h>
59 #include <linux/mbcache.h>
60 #include <linux/quotaops.h>
61 #include <linux/rwsem.h>
62 #include <linux/security.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 const 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 const 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 const struct xattr_handler *
129 ext2_xattr_handler(int name_index)
130 {
131         const 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         name_len = strlen(name);
164         if (name_len > 255)
165                 return -ERANGE;
166
167         down_read(&EXT2_I(inode)->xattr_sem);
168         error = -ENODATA;
169         if (!EXT2_I(inode)->i_file_acl)
170                 goto cleanup;
171         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
172         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
173         error = -EIO;
174         if (!bh)
175                 goto cleanup;
176         ea_bdebug(bh, "b_count=%d, refcount=%d",
177                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
178         end = bh->b_data + bh->b_size;
179         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
180             HDR(bh)->h_blocks != cpu_to_le32(1)) {
181 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_get",
182                         "inode %ld: bad block %d", inode->i_ino,
183                         EXT2_I(inode)->i_file_acl);
184                 error = -EIO;
185                 goto cleanup;
186         }
187
188         /* find named attribute */
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         if (ext2_xattr_cache_insert(bh))
202                 ea_idebug(inode, "cache insert failed");
203         error = -ENODATA;
204         goto cleanup;
205 found:
206         /* check the buffer size */
207         if (entry->e_value_block != 0)
208                 goto bad_block;
209         size = le32_to_cpu(entry->e_value_size);
210         if (size > inode->i_sb->s_blocksize ||
211             le16_to_cpu(entry->e_value_offs) + size > inode->i_sb->s_blocksize)
212                 goto bad_block;
213
214         if (ext2_xattr_cache_insert(bh))
215                 ea_idebug(inode, "cache insert failed");
216         if (buffer) {
217                 error = -ERANGE;
218                 if (size > buffer_size)
219                         goto cleanup;
220                 /* return value of attribute */
221                 memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
222                         size);
223         }
224         error = size;
225
226 cleanup:
227         brelse(bh);
228         up_read(&EXT2_I(inode)->xattr_sem);
229
230         return error;
231 }
232
233 /*
234  * ext2_xattr_list()
235  *
236  * Copy a list of attribute names into the buffer
237  * provided, or compute the buffer size required.
238  * Buffer is NULL to compute the size of the buffer required.
239  *
240  * Returns a negative error number on failure, or the number of bytes
241  * used / required on success.
242  */
243 static int
244 ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
245 {
246         struct inode *inode = dentry->d_inode;
247         struct buffer_head *bh = NULL;
248         struct ext2_xattr_entry *entry;
249         char *end;
250         size_t rest = buffer_size;
251         int error;
252
253         ea_idebug(inode, "buffer=%p, buffer_size=%ld",
254                   buffer, (long)buffer_size);
255
256         down_read(&EXT2_I(inode)->xattr_sem);
257         error = 0;
258         if (!EXT2_I(inode)->i_file_acl)
259                 goto cleanup;
260         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
261         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
262         error = -EIO;
263         if (!bh)
264                 goto cleanup;
265         ea_bdebug(bh, "b_count=%d, refcount=%d",
266                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
267         end = bh->b_data + bh->b_size;
268         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
269             HDR(bh)->h_blocks != cpu_to_le32(1)) {
270 bad_block:      ext2_error(inode->i_sb, "ext2_xattr_list",
271                         "inode %ld: bad block %d", inode->i_ino,
272                         EXT2_I(inode)->i_file_acl);
273                 error = -EIO;
274                 goto cleanup;
275         }
276
277         /* check the on-disk data structure */
278         entry = FIRST_ENTRY(bh);
279         while (!IS_LAST_ENTRY(entry)) {
280                 struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(entry);
281
282                 if ((char *)next >= end)
283                         goto bad_block;
284                 entry = next;
285         }
286         if (ext2_xattr_cache_insert(bh))
287                 ea_idebug(inode, "cache insert failed");
288
289         /* list the attribute names */
290         for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
291              entry = EXT2_XATTR_NEXT(entry)) {
292                 const struct xattr_handler *handler =
293                         ext2_xattr_handler(entry->e_name_index);
294
295                 if (handler) {
296                         size_t size = handler->list(dentry, buffer, rest,
297                                                     entry->e_name,
298                                                     entry->e_name_len,
299                                                     handler->flags);
300                         if (buffer) {
301                                 if (size > rest) {
302                                         error = -ERANGE;
303                                         goto cleanup;
304                                 }
305                                 buffer += size;
306                         }
307                         rest -= size;
308                 }
309         }
310         error = buffer_size - rest;  /* total size */
311
312 cleanup:
313         brelse(bh);
314         up_read(&EXT2_I(inode)->xattr_sem);
315
316         return error;
317 }
318
319 /*
320  * Inode operation listxattr()
321  *
322  * dentry->d_inode->i_mutex: don't care
323  */
324 ssize_t
325 ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
326 {
327         return ext2_xattr_list(dentry, buffer, size);
328 }
329
330 /*
331  * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
332  * not set, set it.
333  */
334 static void ext2_xattr_update_super_block(struct super_block *sb)
335 {
336         if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
337                 return;
338
339         spin_lock(&EXT2_SB(sb)->s_lock);
340         EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
341         spin_unlock(&EXT2_SB(sb)->s_lock);
342         mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
343 }
344
345 /*
346  * ext2_xattr_set()
347  *
348  * Create, replace or remove an extended attribute for this inode.  Value
349  * is NULL to remove an existing extended attribute, and non-NULL to
350  * either replace an existing extended attribute, or create a new extended
351  * attribute. The flags XATTR_REPLACE and XATTR_CREATE
352  * specify that an extended attribute must exist and must not exist
353  * previous to the call, respectively.
354  *
355  * Returns 0, or a negative error number on failure.
356  */
357 int
358 ext2_xattr_set(struct inode *inode, int name_index, const char *name,
359                const void *value, size_t value_len, int flags)
360 {
361         struct super_block *sb = inode->i_sb;
362         struct buffer_head *bh = NULL;
363         struct ext2_xattr_header *header = NULL;
364         struct ext2_xattr_entry *here, *last;
365         size_t name_len, free, min_offs = sb->s_blocksize;
366         int not_found = 1, error;
367         char *end;
368         
369         /*
370          * header -- Points either into bh, or to a temporarily
371          *           allocated buffer.
372          * here -- The named entry found, or the place for inserting, within
373          *         the block pointed to by header.
374          * last -- Points right after the last named entry within the block
375          *         pointed to by header.
376          * min_offs -- The offset of the first value (values are aligned
377          *             towards the end of the block).
378          * end -- Points right after the block pointed to by header.
379          */
380         
381         ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
382                   name_index, name, value, (long)value_len);
383
384         if (value == NULL)
385                 value_len = 0;
386         if (name == NULL)
387                 return -EINVAL;
388         name_len = strlen(name);
389         if (name_len > 255 || value_len > sb->s_blocksize)
390                 return -ERANGE;
391         down_write(&EXT2_I(inode)->xattr_sem);
392         if (EXT2_I(inode)->i_file_acl) {
393                 /* The inode already has an extended attribute block. */
394                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
395                 error = -EIO;
396                 if (!bh)
397                         goto cleanup;
398                 ea_bdebug(bh, "b_count=%d, refcount=%d",
399                         atomic_read(&(bh->b_count)),
400                         le32_to_cpu(HDR(bh)->h_refcount));
401                 header = HDR(bh);
402                 end = bh->b_data + bh->b_size;
403                 if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
404                     header->h_blocks != cpu_to_le32(1)) {
405 bad_block:              ext2_error(sb, "ext2_xattr_set",
406                                 "inode %ld: bad block %d", inode->i_ino, 
407                                    EXT2_I(inode)->i_file_acl);
408                         error = -EIO;
409                         goto cleanup;
410                 }
411                 /* Find the named attribute. */
412                 here = FIRST_ENTRY(bh);
413                 while (!IS_LAST_ENTRY(here)) {
414                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
415                         if ((char *)next >= end)
416                                 goto bad_block;
417                         if (!here->e_value_block && here->e_value_size) {
418                                 size_t offs = le16_to_cpu(here->e_value_offs);
419                                 if (offs < min_offs)
420                                         min_offs = offs;
421                         }
422                         not_found = name_index - here->e_name_index;
423                         if (!not_found)
424                                 not_found = name_len - here->e_name_len;
425                         if (!not_found)
426                                 not_found = memcmp(name, here->e_name,name_len);
427                         if (not_found <= 0)
428                                 break;
429                         here = next;
430                 }
431                 last = here;
432                 /* We still need to compute min_offs and last. */
433                 while (!IS_LAST_ENTRY(last)) {
434                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
435                         if ((char *)next >= end)
436                                 goto bad_block;
437                         if (!last->e_value_block && last->e_value_size) {
438                                 size_t offs = le16_to_cpu(last->e_value_offs);
439                                 if (offs < min_offs)
440                                         min_offs = offs;
441                         }
442                         last = next;
443                 }
444
445                 /* Check whether we have enough space left. */
446                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
447         } else {
448                 /* We will use a new extended attribute block. */
449                 free = sb->s_blocksize -
450                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
451                 here = last = NULL;  /* avoid gcc uninitialized warning. */
452         }
453
454         if (not_found) {
455                 /* Request to remove a nonexistent attribute? */
456                 error = -ENODATA;
457                 if (flags & XATTR_REPLACE)
458                         goto cleanup;
459                 error = 0;
460                 if (value == NULL)
461                         goto cleanup;
462         } else {
463                 /* Request to create an existing attribute? */
464                 error = -EEXIST;
465                 if (flags & XATTR_CREATE)
466                         goto cleanup;
467                 if (!here->e_value_block && here->e_value_size) {
468                         size_t size = le32_to_cpu(here->e_value_size);
469
470                         if (le16_to_cpu(here->e_value_offs) + size > 
471                             sb->s_blocksize || size > sb->s_blocksize)
472                                 goto bad_block;
473                         free += EXT2_XATTR_SIZE(size);
474                 }
475                 free += EXT2_XATTR_LEN(name_len);
476         }
477         error = -ENOSPC;
478         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
479                 goto cleanup;
480
481         /* Here we know that we can set the new attribute. */
482
483         if (header) {
484                 struct mb_cache_entry *ce;
485
486                 /* assert(header == HDR(bh)); */
487                 ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev,
488                                         bh->b_blocknr);
489                 lock_buffer(bh);
490                 if (header->h_refcount == cpu_to_le32(1)) {
491                         ea_bdebug(bh, "modifying in-place");
492                         if (ce)
493                                 mb_cache_entry_free(ce);
494                         /* keep the buffer locked while modifying it. */
495                 } else {
496                         int offset;
497
498                         if (ce)
499                                 mb_cache_entry_release(ce);
500                         unlock_buffer(bh);
501                         ea_bdebug(bh, "cloning");
502                         header = kmalloc(bh->b_size, GFP_KERNEL);
503                         error = -ENOMEM;
504                         if (header == NULL)
505                                 goto cleanup;
506                         memcpy(header, HDR(bh), bh->b_size);
507                         header->h_refcount = cpu_to_le32(1);
508
509                         offset = (char *)here - bh->b_data;
510                         here = ENTRY((char *)header + offset);
511                         offset = (char *)last - bh->b_data;
512                         last = ENTRY((char *)header + offset);
513                 }
514         } else {
515                 /* Allocate a buffer where we construct the new block. */
516                 header = kzalloc(sb->s_blocksize, GFP_KERNEL);
517                 error = -ENOMEM;
518                 if (header == NULL)
519                         goto cleanup;
520                 end = (char *)header + sb->s_blocksize;
521                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
522                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
523                 last = here = ENTRY(header+1);
524         }
525
526         /* Iff we are modifying the block in-place, bh is locked here. */
527
528         if (not_found) {
529                 /* Insert the new name. */
530                 size_t size = EXT2_XATTR_LEN(name_len);
531                 size_t rest = (char *)last - (char *)here;
532                 memmove((char *)here + size, here, rest);
533                 memset(here, 0, size);
534                 here->e_name_index = name_index;
535                 here->e_name_len = name_len;
536                 memcpy(here->e_name, name, name_len);
537         } else {
538                 if (!here->e_value_block && here->e_value_size) {
539                         char *first_val = (char *)header + min_offs;
540                         size_t offs = le16_to_cpu(here->e_value_offs);
541                         char *val = (char *)header + offs;
542                         size_t size = EXT2_XATTR_SIZE(
543                                 le32_to_cpu(here->e_value_size));
544
545                         if (size == EXT2_XATTR_SIZE(value_len)) {
546                                 /* The old and the new value have the same
547                                    size. Just replace. */
548                                 here->e_value_size = cpu_to_le32(value_len);
549                                 memset(val + size - EXT2_XATTR_PAD, 0,
550                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
551                                 memcpy(val, value, value_len);
552                                 goto skip_replace;
553                         }
554
555                         /* Remove the old value. */
556                         memmove(first_val + size, first_val, val - first_val);
557                         memset(first_val, 0, size);
558                         here->e_value_offs = 0;
559                         min_offs += size;
560
561                         /* Adjust all value offsets. */
562                         last = ENTRY(header+1);
563                         while (!IS_LAST_ENTRY(last)) {
564                                 size_t o = le16_to_cpu(last->e_value_offs);
565                                 if (!last->e_value_block && o < offs)
566                                         last->e_value_offs =
567                                                 cpu_to_le16(o + size);
568                                 last = EXT2_XATTR_NEXT(last);
569                         }
570                 }
571                 if (value == NULL) {
572                         /* Remove the old name. */
573                         size_t size = EXT2_XATTR_LEN(name_len);
574                         last = ENTRY((char *)last - size);
575                         memmove(here, (char*)here + size,
576                                 (char*)last - (char*)here);
577                         memset(last, 0, size);
578                 }
579         }
580
581         if (value != NULL) {
582                 /* Insert the new value. */
583                 here->e_value_size = cpu_to_le32(value_len);
584                 if (value_len) {
585                         size_t size = EXT2_XATTR_SIZE(value_len);
586                         char *val = (char *)header + min_offs - size;
587                         here->e_value_offs =
588                                 cpu_to_le16((char *)val - (char *)header);
589                         memset(val + size - EXT2_XATTR_PAD, 0,
590                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
591                         memcpy(val, value, value_len);
592                 }
593         }
594
595 skip_replace:
596         if (IS_LAST_ENTRY(ENTRY(header+1))) {
597                 /* This block is now empty. */
598                 if (bh && header == HDR(bh))
599                         unlock_buffer(bh);  /* we were modifying in-place. */
600                 error = ext2_xattr_set2(inode, bh, NULL);
601         } else {
602                 ext2_xattr_rehash(header, here);
603                 if (bh && header == HDR(bh))
604                         unlock_buffer(bh);  /* we were modifying in-place. */
605                 error = ext2_xattr_set2(inode, bh, header);
606         }
607
608 cleanup:
609         brelse(bh);
610         if (!(bh && header == HDR(bh)))
611                 kfree(header);
612         up_write(&EXT2_I(inode)->xattr_sem);
613
614         return error;
615 }
616
617 /*
618  * Second half of ext2_xattr_set(): Update the file system.
619  */
620 static int
621 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
622                 struct ext2_xattr_header *header)
623 {
624         struct super_block *sb = inode->i_sb;
625         struct buffer_head *new_bh = NULL;
626         int error;
627
628         if (header) {
629                 new_bh = ext2_xattr_cache_find(inode, header);
630                 if (new_bh) {
631                         /* We found an identical block in the cache. */
632                         if (new_bh == old_bh) {
633                                 ea_bdebug(new_bh, "keeping this block");
634                         } else {
635                                 /* The old block is released after updating
636                                    the inode.  */
637                                 ea_bdebug(new_bh, "reusing block");
638
639                                 error = dquot_alloc_block(inode, 1);
640                                 if (error) {
641                                         unlock_buffer(new_bh);
642                                         goto cleanup;
643                                 }
644                                 le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
645                                 ea_bdebug(new_bh, "refcount now=%d",
646                                         le32_to_cpu(HDR(new_bh)->h_refcount));
647                         }
648                         unlock_buffer(new_bh);
649                 } else if (old_bh && header == HDR(old_bh)) {
650                         /* Keep this block. No need to lock the block as we
651                            don't need to change the reference count. */
652                         new_bh = old_bh;
653                         get_bh(new_bh);
654                         ext2_xattr_cache_insert(new_bh);
655                 } else {
656                         /* We need to allocate a new block */
657                         ext2_fsblk_t goal = ext2_group_first_block_no(sb,
658                                                 EXT2_I(inode)->i_block_group);
659                         int block = ext2_new_block(inode, goal, &error);
660                         if (error)
661                                 goto cleanup;
662                         ea_idebug(inode, "creating block %d", block);
663
664                         new_bh = sb_getblk(sb, block);
665                         if (unlikely(!new_bh)) {
666                                 ext2_free_blocks(inode, block, 1);
667                                 mark_inode_dirty(inode);
668                                 error = -ENOMEM;
669                                 goto cleanup;
670                         }
671                         lock_buffer(new_bh);
672                         memcpy(new_bh->b_data, header, new_bh->b_size);
673                         set_buffer_uptodate(new_bh);
674                         unlock_buffer(new_bh);
675                         ext2_xattr_cache_insert(new_bh);
676                         
677                         ext2_xattr_update_super_block(sb);
678                 }
679                 mark_buffer_dirty(new_bh);
680                 if (IS_SYNC(inode)) {
681                         sync_dirty_buffer(new_bh);
682                         error = -EIO;
683                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
684                                 goto cleanup;
685                 }
686         }
687
688         /* Update the inode. */
689         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
690         inode->i_ctime = CURRENT_TIME_SEC;
691         if (IS_SYNC(inode)) {
692                 error = sync_inode_metadata(inode, 1);
693                 /* In case sync failed due to ENOSPC the inode was actually
694                  * written (only some dirty data were not) so we just proceed
695                  * as if nothing happened and cleanup the unused block */
696                 if (error && error != -ENOSPC) {
697                         if (new_bh && new_bh != old_bh) {
698                                 dquot_free_block_nodirty(inode, 1);
699                                 mark_inode_dirty(inode);
700                         }
701                         goto cleanup;
702                 }
703         } else
704                 mark_inode_dirty(inode);
705
706         error = 0;
707         if (old_bh && old_bh != new_bh) {
708                 struct mb_cache_entry *ce;
709
710                 /*
711                  * If there was an old block and we are no longer using it,
712                  * release the old block.
713                  */
714                 ce = mb_cache_entry_get(ext2_xattr_cache, old_bh->b_bdev,
715                                         old_bh->b_blocknr);
716                 lock_buffer(old_bh);
717                 if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
718                         /* Free the old block. */
719                         if (ce)
720                                 mb_cache_entry_free(ce);
721                         ea_bdebug(old_bh, "freeing");
722                         ext2_free_blocks(inode, old_bh->b_blocknr, 1);
723                         mark_inode_dirty(inode);
724                         /* We let our caller release old_bh, so we
725                          * need to duplicate the buffer before. */
726                         get_bh(old_bh);
727                         bforget(old_bh);
728                 } else {
729                         /* Decrement the refcount only. */
730                         le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
731                         if (ce)
732                                 mb_cache_entry_release(ce);
733                         dquot_free_block_nodirty(inode, 1);
734                         mark_inode_dirty(inode);
735                         mark_buffer_dirty(old_bh);
736                         ea_bdebug(old_bh, "refcount now=%d",
737                                 le32_to_cpu(HDR(old_bh)->h_refcount));
738                 }
739                 unlock_buffer(old_bh);
740         }
741
742 cleanup:
743         brelse(new_bh);
744
745         return error;
746 }
747
748 /*
749  * ext2_xattr_delete_inode()
750  *
751  * Free extended attribute resources associated with this inode. This
752  * is called immediately before an inode is freed.
753  */
754 void
755 ext2_xattr_delete_inode(struct inode *inode)
756 {
757         struct buffer_head *bh = NULL;
758         struct mb_cache_entry *ce;
759
760         down_write(&EXT2_I(inode)->xattr_sem);
761         if (!EXT2_I(inode)->i_file_acl)
762                 goto cleanup;
763         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
764         if (!bh) {
765                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
766                         "inode %ld: block %d read error", inode->i_ino,
767                         EXT2_I(inode)->i_file_acl);
768                 goto cleanup;
769         }
770         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
771         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
772             HDR(bh)->h_blocks != cpu_to_le32(1)) {
773                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
774                         "inode %ld: bad block %d", inode->i_ino,
775                         EXT2_I(inode)->i_file_acl);
776                 goto cleanup;
777         }
778         ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev, bh->b_blocknr);
779         lock_buffer(bh);
780         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
781                 if (ce)
782                         mb_cache_entry_free(ce);
783                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
784                 get_bh(bh);
785                 bforget(bh);
786                 unlock_buffer(bh);
787         } else {
788                 le32_add_cpu(&HDR(bh)->h_refcount, -1);
789                 if (ce)
790                         mb_cache_entry_release(ce);
791                 ea_bdebug(bh, "refcount now=%d",
792                         le32_to_cpu(HDR(bh)->h_refcount));
793                 unlock_buffer(bh);
794                 mark_buffer_dirty(bh);
795                 if (IS_SYNC(inode))
796                         sync_dirty_buffer(bh);
797                 dquot_free_block_nodirty(inode, 1);
798         }
799         EXT2_I(inode)->i_file_acl = 0;
800
801 cleanup:
802         brelse(bh);
803         up_write(&EXT2_I(inode)->xattr_sem);
804 }
805
806 /*
807  * ext2_xattr_put_super()
808  *
809  * This is called when a file system is unmounted.
810  */
811 void
812 ext2_xattr_put_super(struct super_block *sb)
813 {
814         mb_cache_shrink(sb->s_bdev);
815 }
816
817
818 /*
819  * ext2_xattr_cache_insert()
820  *
821  * Create a new entry in the extended attribute cache, and insert
822  * it unless such an entry is already in the cache.
823  *
824  * Returns 0, or a negative error number on failure.
825  */
826 static int
827 ext2_xattr_cache_insert(struct buffer_head *bh)
828 {
829         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
830         struct mb_cache_entry *ce;
831         int error;
832
833         ce = mb_cache_entry_alloc(ext2_xattr_cache, GFP_NOFS);
834         if (!ce)
835                 return -ENOMEM;
836         error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, hash);
837         if (error) {
838                 mb_cache_entry_free(ce);
839                 if (error == -EBUSY) {
840                         ea_bdebug(bh, "already in cache (%d cache entries)",
841                                 atomic_read(&ext2_xattr_cache->c_entry_count));
842                         error = 0;
843                 }
844         } else {
845                 ea_bdebug(bh, "inserting [%x] (%d cache entries)", (int)hash,
846                           atomic_read(&ext2_xattr_cache->c_entry_count));
847                 mb_cache_entry_release(ce);
848         }
849         return error;
850 }
851
852 /*
853  * ext2_xattr_cmp()
854  *
855  * Compare two extended attribute blocks for equality.
856  *
857  * Returns 0 if the blocks are equal, 1 if they differ, and
858  * a negative error number on errors.
859  */
860 static int
861 ext2_xattr_cmp(struct ext2_xattr_header *header1,
862                struct ext2_xattr_header *header2)
863 {
864         struct ext2_xattr_entry *entry1, *entry2;
865
866         entry1 = ENTRY(header1+1);
867         entry2 = ENTRY(header2+1);
868         while (!IS_LAST_ENTRY(entry1)) {
869                 if (IS_LAST_ENTRY(entry2))
870                         return 1;
871                 if (entry1->e_hash != entry2->e_hash ||
872                     entry1->e_name_index != entry2->e_name_index ||
873                     entry1->e_name_len != entry2->e_name_len ||
874                     entry1->e_value_size != entry2->e_value_size ||
875                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
876                         return 1;
877                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
878                         return -EIO;
879                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
880                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
881                            le32_to_cpu(entry1->e_value_size)))
882                         return 1;
883
884                 entry1 = EXT2_XATTR_NEXT(entry1);
885                 entry2 = EXT2_XATTR_NEXT(entry2);
886         }
887         if (!IS_LAST_ENTRY(entry2))
888                 return 1;
889         return 0;
890 }
891
892 /*
893  * ext2_xattr_cache_find()
894  *
895  * Find an identical extended attribute block.
896  *
897  * Returns a locked buffer head to the block found, or NULL if such
898  * a block was not found or an error occurred.
899  */
900 static struct buffer_head *
901 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
902 {
903         __u32 hash = le32_to_cpu(header->h_hash);
904         struct mb_cache_entry *ce;
905
906         if (!header->h_hash)
907                 return NULL;  /* never share */
908         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
909 again:
910         ce = mb_cache_entry_find_first(ext2_xattr_cache, inode->i_sb->s_bdev,
911                                        hash);
912         while (ce) {
913                 struct buffer_head *bh;
914
915                 if (IS_ERR(ce)) {
916                         if (PTR_ERR(ce) == -EAGAIN)
917                                 goto again;
918                         break;
919                 }
920
921                 bh = sb_bread(inode->i_sb, ce->e_block);
922                 if (!bh) {
923                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
924                                 "inode %ld: block %ld read error",
925                                 inode->i_ino, (unsigned long) ce->e_block);
926                 } else {
927                         lock_buffer(bh);
928                         if (le32_to_cpu(HDR(bh)->h_refcount) >
929                                    EXT2_XATTR_REFCOUNT_MAX) {
930                                 ea_idebug(inode, "block %ld refcount %d>%d",
931                                           (unsigned long) ce->e_block,
932                                           le32_to_cpu(HDR(bh)->h_refcount),
933                                           EXT2_XATTR_REFCOUNT_MAX);
934                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
935                                 ea_bdebug(bh, "b_count=%d",
936                                           atomic_read(&(bh->b_count)));
937                                 mb_cache_entry_release(ce);
938                                 return bh;
939                         }
940                         unlock_buffer(bh);
941                         brelse(bh);
942                 }
943                 ce = mb_cache_entry_find_next(ce, inode->i_sb->s_bdev, hash);
944         }
945         return NULL;
946 }
947
948 #define NAME_HASH_SHIFT 5
949 #define VALUE_HASH_SHIFT 16
950
951 /*
952  * ext2_xattr_hash_entry()
953  *
954  * Compute the hash of an extended attribute.
955  */
956 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
957                                          struct ext2_xattr_entry *entry)
958 {
959         __u32 hash = 0;
960         char *name = entry->e_name;
961         int n;
962
963         for (n=0; n < entry->e_name_len; n++) {
964                 hash = (hash << NAME_HASH_SHIFT) ^
965                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
966                        *name++;
967         }
968
969         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
970                 __le32 *value = (__le32 *)((char *)header +
971                         le16_to_cpu(entry->e_value_offs));
972                 for (n = (le32_to_cpu(entry->e_value_size) +
973                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
974                         hash = (hash << VALUE_HASH_SHIFT) ^
975                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
976                                le32_to_cpu(*value++);
977                 }
978         }
979         entry->e_hash = cpu_to_le32(hash);
980 }
981
982 #undef NAME_HASH_SHIFT
983 #undef VALUE_HASH_SHIFT
984
985 #define BLOCK_HASH_SHIFT 16
986
987 /*
988  * ext2_xattr_rehash()
989  *
990  * Re-compute the extended attribute hash value after an entry has changed.
991  */
992 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
993                               struct ext2_xattr_entry *entry)
994 {
995         struct ext2_xattr_entry *here;
996         __u32 hash = 0;
997         
998         ext2_xattr_hash_entry(header, entry);
999         here = ENTRY(header+1);
1000         while (!IS_LAST_ENTRY(here)) {
1001                 if (!here->e_hash) {
1002                         /* Block is not shared if an entry's hash value == 0 */
1003                         hash = 0;
1004                         break;
1005                 }
1006                 hash = (hash << BLOCK_HASH_SHIFT) ^
1007                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1008                        le32_to_cpu(here->e_hash);
1009                 here = EXT2_XATTR_NEXT(here);
1010         }
1011         header->h_hash = cpu_to_le32(hash);
1012 }
1013
1014 #undef BLOCK_HASH_SHIFT
1015
1016 int __init
1017 init_ext2_xattr(void)
1018 {
1019         ext2_xattr_cache = mb_cache_create("ext2_xattr", 6);
1020         if (!ext2_xattr_cache)
1021                 return -ENOMEM;
1022         return 0;
1023 }
1024
1025 void
1026 exit_ext2_xattr(void)
1027 {
1028         mb_cache_destroy(ext2_xattr_cache);
1029 }