27982b500e84a972412e2731125b70c30df7a36c
[linux-2.6.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 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_sem: 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 (IS_RDONLY(inode))
393                 return -EROFS;
394         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
395                 return -EPERM;
396         if (value == NULL)
397                 value_len = 0;
398         if (name == NULL)
399                 return -EINVAL;
400         name_len = strlen(name);
401         if (name_len > 255 || value_len > sb->s_blocksize)
402                 return -ERANGE;
403         down_write(&EXT2_I(inode)->xattr_sem);
404         if (EXT2_I(inode)->i_file_acl) {
405                 /* The inode already has an extended attribute block. */
406                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
407                 error = -EIO;
408                 if (!bh)
409                         goto cleanup;
410                 ea_bdebug(bh, "b_count=%d, refcount=%d",
411                         atomic_read(&(bh->b_count)),
412                         le32_to_cpu(HDR(bh)->h_refcount));
413                 header = HDR(bh);
414                 end = bh->b_data + bh->b_size;
415                 if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
416                     header->h_blocks != cpu_to_le32(1)) {
417 bad_block:              ext2_error(sb, "ext2_xattr_set",
418                                 "inode %ld: bad block %d", inode->i_ino, 
419                                    EXT2_I(inode)->i_file_acl);
420                         error = -EIO;
421                         goto cleanup;
422                 }
423                 /* Find the named attribute. */
424                 here = FIRST_ENTRY(bh);
425                 while (!IS_LAST_ENTRY(here)) {
426                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
427                         if ((char *)next >= end)
428                                 goto bad_block;
429                         if (!here->e_value_block && here->e_value_size) {
430                                 size_t offs = le16_to_cpu(here->e_value_offs);
431                                 if (offs < min_offs)
432                                         min_offs = offs;
433                         }
434                         not_found = name_index - here->e_name_index;
435                         if (!not_found)
436                                 not_found = name_len - here->e_name_len;
437                         if (!not_found)
438                                 not_found = memcmp(name, here->e_name,name_len);
439                         if (not_found <= 0)
440                                 break;
441                         here = next;
442                 }
443                 last = here;
444                 /* We still need to compute min_offs and last. */
445                 while (!IS_LAST_ENTRY(last)) {
446                         struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
447                         if ((char *)next >= end)
448                                 goto bad_block;
449                         if (!last->e_value_block && last->e_value_size) {
450                                 size_t offs = le16_to_cpu(last->e_value_offs);
451                                 if (offs < min_offs)
452                                         min_offs = offs;
453                         }
454                         last = next;
455                 }
456
457                 /* Check whether we have enough space left. */
458                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
459         } else {
460                 /* We will use a new extended attribute block. */
461                 free = sb->s_blocksize -
462                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
463                 here = last = NULL;  /* avoid gcc uninitialized warning. */
464         }
465
466         if (not_found) {
467                 /* Request to remove a nonexistent attribute? */
468                 error = -ENODATA;
469                 if (flags & XATTR_REPLACE)
470                         goto cleanup;
471                 error = 0;
472                 if (value == NULL)
473                         goto cleanup;
474         } else {
475                 /* Request to create an existing attribute? */
476                 error = -EEXIST;
477                 if (flags & XATTR_CREATE)
478                         goto cleanup;
479                 if (!here->e_value_block && here->e_value_size) {
480                         size_t size = le32_to_cpu(here->e_value_size);
481
482                         if (le16_to_cpu(here->e_value_offs) + size > 
483                             sb->s_blocksize || size > sb->s_blocksize)
484                                 goto bad_block;
485                         free += EXT2_XATTR_SIZE(size);
486                 }
487                 free += EXT2_XATTR_LEN(name_len);
488         }
489         error = -ENOSPC;
490         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
491                 goto cleanup;
492
493         /* Here we know that we can set the new attribute. */
494
495         if (header) {
496                 struct mb_cache_entry *ce;
497
498                 /* assert(header == HDR(bh)); */
499                 ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev,
500                                         bh->b_blocknr);
501                 lock_buffer(bh);
502                 if (header->h_refcount == cpu_to_le32(1)) {
503                         ea_bdebug(bh, "modifying in-place");
504                         if (ce)
505                                 mb_cache_entry_free(ce);
506                         /* keep the buffer locked while modifying it. */
507                 } else {
508                         int offset;
509
510                         if (ce)
511                                 mb_cache_entry_release(ce);
512                         unlock_buffer(bh);
513                         ea_bdebug(bh, "cloning");
514                         header = kmalloc(bh->b_size, GFP_KERNEL);
515                         error = -ENOMEM;
516                         if (header == NULL)
517                                 goto cleanup;
518                         memcpy(header, HDR(bh), bh->b_size);
519                         header->h_refcount = cpu_to_le32(1);
520
521                         offset = (char *)here - bh->b_data;
522                         here = ENTRY((char *)header + offset);
523                         offset = (char *)last - bh->b_data;
524                         last = ENTRY((char *)header + offset);
525                 }
526         } else {
527                 /* Allocate a buffer where we construct the new block. */
528                 header = kmalloc(sb->s_blocksize, GFP_KERNEL);
529                 error = -ENOMEM;
530                 if (header == NULL)
531                         goto cleanup;
532                 memset(header, 0, sb->s_blocksize);
533                 end = (char *)header + sb->s_blocksize;
534                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
535                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
536                 last = here = ENTRY(header+1);
537         }
538
539         /* Iff we are modifying the block in-place, bh is locked here. */
540
541         if (not_found) {
542                 /* Insert the new name. */
543                 size_t size = EXT2_XATTR_LEN(name_len);
544                 size_t rest = (char *)last - (char *)here;
545                 memmove((char *)here + size, here, rest);
546                 memset(here, 0, size);
547                 here->e_name_index = name_index;
548                 here->e_name_len = name_len;
549                 memcpy(here->e_name, name, name_len);
550         } else {
551                 if (!here->e_value_block && here->e_value_size) {
552                         char *first_val = (char *)header + min_offs;
553                         size_t offs = le16_to_cpu(here->e_value_offs);
554                         char *val = (char *)header + offs;
555                         size_t size = EXT2_XATTR_SIZE(
556                                 le32_to_cpu(here->e_value_size));
557
558                         if (size == EXT2_XATTR_SIZE(value_len)) {
559                                 /* The old and the new value have the same
560                                    size. Just replace. */
561                                 here->e_value_size = cpu_to_le32(value_len);
562                                 memset(val + size - EXT2_XATTR_PAD, 0,
563                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
564                                 memcpy(val, value, value_len);
565                                 goto skip_replace;
566                         }
567
568                         /* Remove the old value. */
569                         memmove(first_val + size, first_val, val - first_val);
570                         memset(first_val, 0, size);
571                         here->e_value_offs = 0;
572                         min_offs += size;
573
574                         /* Adjust all value offsets. */
575                         last = ENTRY(header+1);
576                         while (!IS_LAST_ENTRY(last)) {
577                                 size_t o = le16_to_cpu(last->e_value_offs);
578                                 if (!last->e_value_block && o < offs)
579                                         last->e_value_offs =
580                                                 cpu_to_le16(o + size);
581                                 last = EXT2_XATTR_NEXT(last);
582                         }
583                 }
584                 if (value == NULL) {
585                         /* Remove the old name. */
586                         size_t size = EXT2_XATTR_LEN(name_len);
587                         last = ENTRY((char *)last - size);
588                         memmove(here, (char*)here + size,
589                                 (char*)last - (char*)here);
590                         memset(last, 0, size);
591                 }
592         }
593
594         if (value != NULL) {
595                 /* Insert the new value. */
596                 here->e_value_size = cpu_to_le32(value_len);
597                 if (value_len) {
598                         size_t size = EXT2_XATTR_SIZE(value_len);
599                         char *val = (char *)header + min_offs - size;
600                         here->e_value_offs =
601                                 cpu_to_le16((char *)val - (char *)header);
602                         memset(val + size - EXT2_XATTR_PAD, 0,
603                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
604                         memcpy(val, value, value_len);
605                 }
606         }
607
608 skip_replace:
609         if (IS_LAST_ENTRY(ENTRY(header+1))) {
610                 /* This block is now empty. */
611                 if (bh && header == HDR(bh))
612                         unlock_buffer(bh);  /* we were modifying in-place. */
613                 error = ext2_xattr_set2(inode, bh, NULL);
614         } else {
615                 ext2_xattr_rehash(header, here);
616                 if (bh && header == HDR(bh))
617                         unlock_buffer(bh);  /* we were modifying in-place. */
618                 error = ext2_xattr_set2(inode, bh, header);
619         }
620
621 cleanup:
622         brelse(bh);
623         if (!(bh && header == HDR(bh)))
624                 kfree(header);
625         up_write(&EXT2_I(inode)->xattr_sem);
626
627         return error;
628 }
629
630 /*
631  * Second half of ext2_xattr_set(): Update the file system.
632  */
633 static int
634 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
635                 struct ext2_xattr_header *header)
636 {
637         struct super_block *sb = inode->i_sb;
638         struct buffer_head *new_bh = NULL;
639         int error;
640
641         if (header) {
642                 new_bh = ext2_xattr_cache_find(inode, header);
643                 if (new_bh) {
644                         /* We found an identical block in the cache. */
645                         if (new_bh == old_bh) {
646                                 ea_bdebug(new_bh, "keeping this block");
647                         } else {
648                                 /* The old block is released after updating
649                                    the inode.  */
650                                 ea_bdebug(new_bh, "reusing block");
651
652                                 error = -EDQUOT;
653                                 if (DQUOT_ALLOC_BLOCK(inode, 1)) {
654                                         unlock_buffer(new_bh);
655                                         goto cleanup;
656                                 }
657                                 HDR(new_bh)->h_refcount = cpu_to_le32(1 +
658                                         le32_to_cpu(HDR(new_bh)->h_refcount));
659                                 ea_bdebug(new_bh, "refcount now=%d",
660                                         le32_to_cpu(HDR(new_bh)->h_refcount));
661                         }
662                         unlock_buffer(new_bh);
663                 } else if (old_bh && header == HDR(old_bh)) {
664                         /* Keep this block. No need to lock the block as we
665                            don't need to change the reference count. */
666                         new_bh = old_bh;
667                         get_bh(new_bh);
668                         ext2_xattr_cache_insert(new_bh);
669                 } else {
670                         /* We need to allocate a new block */
671                         int goal = le32_to_cpu(EXT2_SB(sb)->s_es->
672                                                            s_first_data_block) +
673                                    EXT2_I(inode)->i_block_group *
674                                    EXT2_BLOCKS_PER_GROUP(sb);
675                         int block = ext2_new_block(inode, goal,
676                                                    NULL, NULL, &error);
677                         if (error)
678                                 goto cleanup;
679                         ea_idebug(inode, "creating block %d", block);
680
681                         new_bh = sb_getblk(sb, block);
682                         if (!new_bh) {
683                                 ext2_free_blocks(inode, block, 1);
684                                 error = -EIO;
685                                 goto cleanup;
686                         }
687                         lock_buffer(new_bh);
688                         memcpy(new_bh->b_data, header, new_bh->b_size);
689                         set_buffer_uptodate(new_bh);
690                         unlock_buffer(new_bh);
691                         ext2_xattr_cache_insert(new_bh);
692                         
693                         ext2_xattr_update_super_block(sb);
694                 }
695                 mark_buffer_dirty(new_bh);
696                 if (IS_SYNC(inode)) {
697                         sync_dirty_buffer(new_bh);
698                         error = -EIO;
699                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
700                                 goto cleanup;
701                 }
702         }
703
704         /* Update the inode. */
705         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
706         inode->i_ctime = CURRENT_TIME_SEC;
707         if (IS_SYNC(inode)) {
708                 error = ext2_sync_inode (inode);
709                 /* In case sync failed due to ENOSPC the inode was actually
710                  * written (only some dirty data were not) so we just proceed
711                  * as if nothing happened and cleanup the unused block */
712                 if (error && error != -ENOSPC) {
713                         if (new_bh && new_bh != old_bh)
714                                 DQUOT_FREE_BLOCK(inode, 1);
715                         goto cleanup;
716                 }
717         } else
718                 mark_inode_dirty(inode);
719
720         error = 0;
721         if (old_bh && old_bh != new_bh) {
722                 struct mb_cache_entry *ce;
723
724                 /*
725                  * If there was an old block and we are no longer using it,
726                  * release the old block.
727                  */
728                 ce = mb_cache_entry_get(ext2_xattr_cache, old_bh->b_bdev,
729                                         old_bh->b_blocknr);
730                 lock_buffer(old_bh);
731                 if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
732                         /* Free the old block. */
733                         if (ce)
734                                 mb_cache_entry_free(ce);
735                         ea_bdebug(old_bh, "freeing");
736                         ext2_free_blocks(inode, old_bh->b_blocknr, 1);
737                         /* We let our caller release old_bh, so we
738                          * need to duplicate the buffer before. */
739                         get_bh(old_bh);
740                         bforget(old_bh);
741                 } else {
742                         /* Decrement the refcount only. */
743                         HDR(old_bh)->h_refcount = cpu_to_le32(
744                                 le32_to_cpu(HDR(old_bh)->h_refcount) - 1);
745                         if (ce)
746                                 mb_cache_entry_release(ce);
747                         DQUOT_FREE_BLOCK(inode, 1);
748                         mark_buffer_dirty(old_bh);
749                         ea_bdebug(old_bh, "refcount now=%d",
750                                 le32_to_cpu(HDR(old_bh)->h_refcount));
751                 }
752                 unlock_buffer(old_bh);
753         }
754
755 cleanup:
756         brelse(new_bh);
757
758         return error;
759 }
760
761 /*
762  * ext2_xattr_delete_inode()
763  *
764  * Free extended attribute resources associated with this inode. This
765  * is called immediately before an inode is freed.
766  */
767 void
768 ext2_xattr_delete_inode(struct inode *inode)
769 {
770         struct buffer_head *bh = NULL;
771         struct mb_cache_entry *ce;
772
773         down_write(&EXT2_I(inode)->xattr_sem);
774         if (!EXT2_I(inode)->i_file_acl)
775                 goto cleanup;
776         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
777         if (!bh) {
778                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
779                         "inode %ld: block %d read error", inode->i_ino,
780                         EXT2_I(inode)->i_file_acl);
781                 goto cleanup;
782         }
783         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
784         if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
785             HDR(bh)->h_blocks != cpu_to_le32(1)) {
786                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
787                         "inode %ld: bad block %d", inode->i_ino,
788                         EXT2_I(inode)->i_file_acl);
789                 goto cleanup;
790         }
791         ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev, bh->b_blocknr);
792         lock_buffer(bh);
793         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
794                 if (ce)
795                         mb_cache_entry_free(ce);
796                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
797                 get_bh(bh);
798                 bforget(bh);
799         } else {
800                 HDR(bh)->h_refcount = cpu_to_le32(
801                         le32_to_cpu(HDR(bh)->h_refcount) - 1);
802                 if (ce)
803                         mb_cache_entry_release(ce);
804                 mark_buffer_dirty(bh);
805                 if (IS_SYNC(inode))
806                         sync_dirty_buffer(bh);
807                 DQUOT_FREE_BLOCK(inode, 1);
808         }
809         ea_bdebug(bh, "refcount now=%d", le32_to_cpu(HDR(bh)->h_refcount) - 1);
810         unlock_buffer(bh);
811         EXT2_I(inode)->i_file_acl = 0;
812
813 cleanup:
814         brelse(bh);
815         up_write(&EXT2_I(inode)->xattr_sem);
816 }
817
818 /*
819  * ext2_xattr_put_super()
820  *
821  * This is called when a file system is unmounted.
822  */
823 void
824 ext2_xattr_put_super(struct super_block *sb)
825 {
826         mb_cache_shrink(ext2_xattr_cache, sb->s_bdev);
827 }
828
829
830 /*
831  * ext2_xattr_cache_insert()
832  *
833  * Create a new entry in the extended attribute cache, and insert
834  * it unless such an entry is already in the cache.
835  *
836  * Returns 0, or a negative error number on failure.
837  */
838 static int
839 ext2_xattr_cache_insert(struct buffer_head *bh)
840 {
841         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
842         struct mb_cache_entry *ce;
843         int error;
844
845         ce = mb_cache_entry_alloc(ext2_xattr_cache);
846         if (!ce)
847                 return -ENOMEM;
848         error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, &hash);
849         if (error) {
850                 mb_cache_entry_free(ce);
851                 if (error == -EBUSY) {
852                         ea_bdebug(bh, "already in cache (%d cache entries)",
853                                 atomic_read(&ext2_xattr_cache->c_entry_count));
854                         error = 0;
855                 }
856         } else {
857                 ea_bdebug(bh, "inserting [%x] (%d cache entries)", (int)hash,
858                           atomic_read(&ext2_xattr_cache->c_entry_count));
859                 mb_cache_entry_release(ce);
860         }
861         return error;
862 }
863
864 /*
865  * ext2_xattr_cmp()
866  *
867  * Compare two extended attribute blocks for equality.
868  *
869  * Returns 0 if the blocks are equal, 1 if they differ, and
870  * a negative error number on errors.
871  */
872 static int
873 ext2_xattr_cmp(struct ext2_xattr_header *header1,
874                struct ext2_xattr_header *header2)
875 {
876         struct ext2_xattr_entry *entry1, *entry2;
877
878         entry1 = ENTRY(header1+1);
879         entry2 = ENTRY(header2+1);
880         while (!IS_LAST_ENTRY(entry1)) {
881                 if (IS_LAST_ENTRY(entry2))
882                         return 1;
883                 if (entry1->e_hash != entry2->e_hash ||
884                     entry1->e_name_index != entry2->e_name_index ||
885                     entry1->e_name_len != entry2->e_name_len ||
886                     entry1->e_value_size != entry2->e_value_size ||
887                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
888                         return 1;
889                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
890                         return -EIO;
891                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
892                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
893                            le32_to_cpu(entry1->e_value_size)))
894                         return 1;
895
896                 entry1 = EXT2_XATTR_NEXT(entry1);
897                 entry2 = EXT2_XATTR_NEXT(entry2);
898         }
899         if (!IS_LAST_ENTRY(entry2))
900                 return 1;
901         return 0;
902 }
903
904 /*
905  * ext2_xattr_cache_find()
906  *
907  * Find an identical extended attribute block.
908  *
909  * Returns a locked buffer head to the block found, or NULL if such
910  * a block was not found or an error occurred.
911  */
912 static struct buffer_head *
913 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
914 {
915         __u32 hash = le32_to_cpu(header->h_hash);
916         struct mb_cache_entry *ce;
917
918         if (!header->h_hash)
919                 return NULL;  /* never share */
920         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
921 again:
922         ce = mb_cache_entry_find_first(ext2_xattr_cache, 0,
923                                        inode->i_sb->s_bdev, hash);
924         while (ce) {
925                 struct buffer_head *bh;
926
927                 if (IS_ERR(ce)) {
928                         if (PTR_ERR(ce) == -EAGAIN)
929                                 goto again;
930                         break;
931                 }
932
933                 bh = sb_bread(inode->i_sb, ce->e_block);
934                 if (!bh) {
935                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
936                                 "inode %ld: block %ld read error",
937                                 inode->i_ino, (unsigned long) ce->e_block);
938                 } else {
939                         lock_buffer(bh);
940                         if (le32_to_cpu(HDR(bh)->h_refcount) >
941                                    EXT2_XATTR_REFCOUNT_MAX) {
942                                 ea_idebug(inode, "block %ld refcount %d>%d",
943                                           (unsigned long) ce->e_block,
944                                           le32_to_cpu(HDR(bh)->h_refcount),
945                                           EXT2_XATTR_REFCOUNT_MAX);
946                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
947                                 ea_bdebug(bh, "b_count=%d",
948                                           atomic_read(&(bh->b_count)));
949                                 mb_cache_entry_release(ce);
950                                 return bh;
951                         }
952                         unlock_buffer(bh);
953                         brelse(bh);
954                 }
955                 ce = mb_cache_entry_find_next(ce, 0, inode->i_sb->s_bdev, hash);
956         }
957         return NULL;
958 }
959
960 #define NAME_HASH_SHIFT 5
961 #define VALUE_HASH_SHIFT 16
962
963 /*
964  * ext2_xattr_hash_entry()
965  *
966  * Compute the hash of an extended attribute.
967  */
968 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
969                                          struct ext2_xattr_entry *entry)
970 {
971         __u32 hash = 0;
972         char *name = entry->e_name;
973         int n;
974
975         for (n=0; n < entry->e_name_len; n++) {
976                 hash = (hash << NAME_HASH_SHIFT) ^
977                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
978                        *name++;
979         }
980
981         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
982                 __le32 *value = (__le32 *)((char *)header +
983                         le16_to_cpu(entry->e_value_offs));
984                 for (n = (le32_to_cpu(entry->e_value_size) +
985                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
986                         hash = (hash << VALUE_HASH_SHIFT) ^
987                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
988                                le32_to_cpu(*value++);
989                 }
990         }
991         entry->e_hash = cpu_to_le32(hash);
992 }
993
994 #undef NAME_HASH_SHIFT
995 #undef VALUE_HASH_SHIFT
996
997 #define BLOCK_HASH_SHIFT 16
998
999 /*
1000  * ext2_xattr_rehash()
1001  *
1002  * Re-compute the extended attribute hash value after an entry has changed.
1003  */
1004 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
1005                               struct ext2_xattr_entry *entry)
1006 {
1007         struct ext2_xattr_entry *here;
1008         __u32 hash = 0;
1009         
1010         ext2_xattr_hash_entry(header, entry);
1011         here = ENTRY(header+1);
1012         while (!IS_LAST_ENTRY(here)) {
1013                 if (!here->e_hash) {
1014                         /* Block is not shared if an entry's hash value == 0 */
1015                         hash = 0;
1016                         break;
1017                 }
1018                 hash = (hash << BLOCK_HASH_SHIFT) ^
1019                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1020                        le32_to_cpu(here->e_hash);
1021                 here = EXT2_XATTR_NEXT(here);
1022         }
1023         header->h_hash = cpu_to_le32(hash);
1024 }
1025
1026 #undef BLOCK_HASH_SHIFT
1027
1028 int __init
1029 init_ext2_xattr(void)
1030 {
1031         ext2_xattr_cache = mb_cache_create("ext2_xattr", NULL,
1032                 sizeof(struct mb_cache_entry) +
1033                 sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]), 1, 6);
1034         if (!ext2_xattr_cache)
1035                 return -ENOMEM;
1036         return 0;
1037 }
1038
1039 void
1040 exit_ext2_xattr(void)
1041 {
1042         mb_cache_destroy(ext2_xattr_cache);
1043 }