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Linux/fs/jbd2/revoke.c

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  1 /*
  2  * linux/fs/jbd2/revoke.c
  3  *
  4  * Written by Stephen C. Tweedie <sct@redhat.com>, 2000
  5  *
  6  * Copyright 2000 Red Hat corp --- All Rights Reserved
  7  *
  8  * This file is part of the Linux kernel and is made available under
  9  * the terms of the GNU General Public License, version 2, or at your
 10  * option, any later version, incorporated herein by reference.
 11  *
 12  * Journal revoke routines for the generic filesystem journaling code;
 13  * part of the ext2fs journaling system.
 14  *
 15  * Revoke is the mechanism used to prevent old log records for deleted
 16  * metadata from being replayed on top of newer data using the same
 17  * blocks.  The revoke mechanism is used in two separate places:
 18  *
 19  * + Commit: during commit we write the entire list of the current
 20  *   transaction's revoked blocks to the journal
 21  *
 22  * + Recovery: during recovery we record the transaction ID of all
 23  *   revoked blocks.  If there are multiple revoke records in the log
 24  *   for a single block, only the last one counts, and if there is a log
 25  *   entry for a block beyond the last revoke, then that log entry still
 26  *   gets replayed.
 27  *
 28  * We can get interactions between revokes and new log data within a
 29  * single transaction:
 30  *
 31  * Block is revoked and then journaled:
 32  *   The desired end result is the journaling of the new block, so we
 33  *   cancel the revoke before the transaction commits.
 34  *
 35  * Block is journaled and then revoked:
 36  *   The revoke must take precedence over the write of the block, so we
 37  *   need either to cancel the journal entry or to write the revoke
 38  *   later in the log than the log block.  In this case, we choose the
 39  *   latter: journaling a block cancels any revoke record for that block
 40  *   in the current transaction, so any revoke for that block in the
 41  *   transaction must have happened after the block was journaled and so
 42  *   the revoke must take precedence.
 43  *
 44  * Block is revoked and then written as data:
 45  *   The data write is allowed to succeed, but the revoke is _not_
 46  *   cancelled.  We still need to prevent old log records from
 47  *   overwriting the new data.  We don't even need to clear the revoke
 48  *   bit here.
 49  *
 50  * We cache revoke status of a buffer in the current transaction in b_states
 51  * bits.  As the name says, revokevalid flag indicates that the cached revoke
 52  * status of a buffer is valid and we can rely on the cached status.
 53  *
 54  * Revoke information on buffers is a tri-state value:
 55  *
 56  * RevokeValid clear:   no cached revoke status, need to look it up
 57  * RevokeValid set, Revoked clear:
 58  *                      buffer has not been revoked, and cancel_revoke
 59  *                      need do nothing.
 60  * RevokeValid set, Revoked set:
 61  *                      buffer has been revoked.
 62  *
 63  * Locking rules:
 64  * We keep two hash tables of revoke records. One hashtable belongs to the
 65  * running transaction (is pointed to by journal->j_revoke), the other one
 66  * belongs to the committing transaction. Accesses to the second hash table
 67  * happen only from the kjournald and no other thread touches this table.  Also
 68  * journal_switch_revoke_table() which switches which hashtable belongs to the
 69  * running and which to the committing transaction is called only from
 70  * kjournald. Therefore we need no locks when accessing the hashtable belonging
 71  * to the committing transaction.
 72  *
 73  * All users operating on the hash table belonging to the running transaction
 74  * have a handle to the transaction. Therefore they are safe from kjournald
 75  * switching hash tables under them. For operations on the lists of entries in
 76  * the hash table j_revoke_lock is used.
 77  *
 78  * Finally, also replay code uses the hash tables but at this moment no one else
 79  * can touch them (filesystem isn't mounted yet) and hence no locking is
 80  * needed.
 81  */
 82 
 83 #ifndef __KERNEL__
 84 #include "jfs_user.h"
 85 #else
 86 #include <linux/time.h>
 87 #include <linux/fs.h>
 88 #include <linux/jbd2.h>
 89 #include <linux/errno.h>
 90 #include <linux/slab.h>
 91 #include <linux/list.h>
 92 #include <linux/init.h>
 93 #include <linux/bio.h>
 94 #include <linux/log2.h>
 95 #include <linux/hash.h>
 96 #endif
 97 
 98 static struct kmem_cache *jbd2_revoke_record_cache;
 99 static struct kmem_cache *jbd2_revoke_table_cache;
100 
101 /* Each revoke record represents one single revoked block.  During
102    journal replay, this involves recording the transaction ID of the
103    last transaction to revoke this block. */
104 
105 struct jbd2_revoke_record_s
106 {
107         struct list_head  hash;
108         tid_t             sequence;     /* Used for recovery only */
109         unsigned long long        blocknr;
110 };
111 
112 
113 /* The revoke table is just a simple hash table of revoke records. */
114 struct jbd2_revoke_table_s
115 {
116         /* It is conceivable that we might want a larger hash table
117          * for recovery.  Must be a power of two. */
118         int               hash_size;
119         int               hash_shift;
120         struct list_head *hash_table;
121 };
122 
123 
124 #ifdef __KERNEL__
125 static void write_one_revoke_record(journal_t *, transaction_t *,
126                                     struct list_head *,
127                                     struct buffer_head **, int *,
128                                     struct jbd2_revoke_record_s *, int);
129 static void flush_descriptor(journal_t *, struct buffer_head *, int, int);
130 #endif
131 
132 /* Utility functions to maintain the revoke table */
133 
134 static inline int hash(journal_t *journal, unsigned long long block)
135 {
136         return hash_64(block, journal->j_revoke->hash_shift);
137 }
138 
139 static int insert_revoke_hash(journal_t *journal, unsigned long long blocknr,
140                               tid_t seq)
141 {
142         struct list_head *hash_list;
143         struct jbd2_revoke_record_s *record;
144         gfp_t gfp_mask = GFP_NOFS;
145 
146         if (journal_oom_retry)
147                 gfp_mask |= __GFP_NOFAIL;
148         record = kmem_cache_alloc(jbd2_revoke_record_cache, gfp_mask);
149         if (!record)
150                 return -ENOMEM;
151 
152         record->sequence = seq;
153         record->blocknr = blocknr;
154         hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
155         spin_lock(&journal->j_revoke_lock);
156         list_add(&record->hash, hash_list);
157         spin_unlock(&journal->j_revoke_lock);
158         return 0;
159 }
160 
161 /* Find a revoke record in the journal's hash table. */
162 
163 static struct jbd2_revoke_record_s *find_revoke_record(journal_t *journal,
164                                                       unsigned long long blocknr)
165 {
166         struct list_head *hash_list;
167         struct jbd2_revoke_record_s *record;
168 
169         hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
170 
171         spin_lock(&journal->j_revoke_lock);
172         record = (struct jbd2_revoke_record_s *) hash_list->next;
173         while (&(record->hash) != hash_list) {
174                 if (record->blocknr == blocknr) {
175                         spin_unlock(&journal->j_revoke_lock);
176                         return record;
177                 }
178                 record = (struct jbd2_revoke_record_s *) record->hash.next;
179         }
180         spin_unlock(&journal->j_revoke_lock);
181         return NULL;
182 }
183 
184 void jbd2_journal_destroy_revoke_caches(void)
185 {
186         if (jbd2_revoke_record_cache) {
187                 kmem_cache_destroy(jbd2_revoke_record_cache);
188                 jbd2_revoke_record_cache = NULL;
189         }
190         if (jbd2_revoke_table_cache) {
191                 kmem_cache_destroy(jbd2_revoke_table_cache);
192                 jbd2_revoke_table_cache = NULL;
193         }
194 }
195 
196 int __init jbd2_journal_init_revoke_caches(void)
197 {
198         J_ASSERT(!jbd2_revoke_record_cache);
199         J_ASSERT(!jbd2_revoke_table_cache);
200 
201         jbd2_revoke_record_cache = KMEM_CACHE(jbd2_revoke_record_s,
202                                         SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY);
203         if (!jbd2_revoke_record_cache)
204                 goto record_cache_failure;
205 
206         jbd2_revoke_table_cache = KMEM_CACHE(jbd2_revoke_table_s,
207                                              SLAB_TEMPORARY);
208         if (!jbd2_revoke_table_cache)
209                 goto table_cache_failure;
210         return 0;
211 table_cache_failure:
212         jbd2_journal_destroy_revoke_caches();
213 record_cache_failure:
214                 return -ENOMEM;
215 }
216 
217 static struct jbd2_revoke_table_s *jbd2_journal_init_revoke_table(int hash_size)
218 {
219         int shift = 0;
220         int tmp = hash_size;
221         struct jbd2_revoke_table_s *table;
222 
223         table = kmem_cache_alloc(jbd2_revoke_table_cache, GFP_KERNEL);
224         if (!table)
225                 goto out;
226 
227         while((tmp >>= 1UL) != 0UL)
228                 shift++;
229 
230         table->hash_size = hash_size;
231         table->hash_shift = shift;
232         table->hash_table =
233                 kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
234         if (!table->hash_table) {
235                 kmem_cache_free(jbd2_revoke_table_cache, table);
236                 table = NULL;
237                 goto out;
238         }
239 
240         for (tmp = 0; tmp < hash_size; tmp++)
241                 INIT_LIST_HEAD(&table->hash_table[tmp]);
242 
243 out:
244         return table;
245 }
246 
247 static void jbd2_journal_destroy_revoke_table(struct jbd2_revoke_table_s *table)
248 {
249         int i;
250         struct list_head *hash_list;
251 
252         for (i = 0; i < table->hash_size; i++) {
253                 hash_list = &table->hash_table[i];
254                 J_ASSERT(list_empty(hash_list));
255         }
256 
257         kfree(table->hash_table);
258         kmem_cache_free(jbd2_revoke_table_cache, table);
259 }
260 
261 /* Initialise the revoke table for a given journal to a given size. */
262 int jbd2_journal_init_revoke(journal_t *journal, int hash_size)
263 {
264         J_ASSERT(journal->j_revoke_table[0] == NULL);
265         J_ASSERT(is_power_of_2(hash_size));
266 
267         journal->j_revoke_table[0] = jbd2_journal_init_revoke_table(hash_size);
268         if (!journal->j_revoke_table[0])
269                 goto fail0;
270 
271         journal->j_revoke_table[1] = jbd2_journal_init_revoke_table(hash_size);
272         if (!journal->j_revoke_table[1])
273                 goto fail1;
274 
275         journal->j_revoke = journal->j_revoke_table[1];
276 
277         spin_lock_init(&journal->j_revoke_lock);
278 
279         return 0;
280 
281 fail1:
282         jbd2_journal_destroy_revoke_table(journal->j_revoke_table[0]);
283 fail0:
284         return -ENOMEM;
285 }
286 
287 /* Destroy a journal's revoke table.  The table must already be empty! */
288 void jbd2_journal_destroy_revoke(journal_t *journal)
289 {
290         journal->j_revoke = NULL;
291         if (journal->j_revoke_table[0])
292                 jbd2_journal_destroy_revoke_table(journal->j_revoke_table[0]);
293         if (journal->j_revoke_table[1])
294                 jbd2_journal_destroy_revoke_table(journal->j_revoke_table[1]);
295 }
296 
297 
298 #ifdef __KERNEL__
299 
300 /*
301  * jbd2_journal_revoke: revoke a given buffer_head from the journal.  This
302  * prevents the block from being replayed during recovery if we take a
303  * crash after this current transaction commits.  Any subsequent
304  * metadata writes of the buffer in this transaction cancel the
305  * revoke.
306  *
307  * Note that this call may block --- it is up to the caller to make
308  * sure that there are no further calls to journal_write_metadata
309  * before the revoke is complete.  In ext3, this implies calling the
310  * revoke before clearing the block bitmap when we are deleting
311  * metadata.
312  *
313  * Revoke performs a jbd2_journal_forget on any buffer_head passed in as a
314  * parameter, but does _not_ forget the buffer_head if the bh was only
315  * found implicitly.
316  *
317  * bh_in may not be a journalled buffer - it may have come off
318  * the hash tables without an attached journal_head.
319  *
320  * If bh_in is non-zero, jbd2_journal_revoke() will decrement its b_count
321  * by one.
322  */
323 
324 int jbd2_journal_revoke(handle_t *handle, unsigned long long blocknr,
325                    struct buffer_head *bh_in)
326 {
327         struct buffer_head *bh = NULL;
328         journal_t *journal;
329         struct block_device *bdev;
330         int err;
331 
332         might_sleep();
333         if (bh_in)
334                 BUFFER_TRACE(bh_in, "enter");
335 
336         journal = handle->h_transaction->t_journal;
337         if (!jbd2_journal_set_features(journal, 0, 0, JBD2_FEATURE_INCOMPAT_REVOKE)){
338                 J_ASSERT (!"Cannot set revoke feature!");
339                 return -EINVAL;
340         }
341 
342         bdev = journal->j_fs_dev;
343         bh = bh_in;
344 
345         if (!bh) {
346                 bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
347                 if (bh)
348                         BUFFER_TRACE(bh, "found on hash");
349         }
350 #ifdef JBD2_EXPENSIVE_CHECKING
351         else {
352                 struct buffer_head *bh2;
353 
354                 /* If there is a different buffer_head lying around in
355                  * memory anywhere... */
356                 bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
357                 if (bh2) {
358                         /* ... and it has RevokeValid status... */
359                         if (bh2 != bh && buffer_revokevalid(bh2))
360                                 /* ...then it better be revoked too,
361                                  * since it's illegal to create a revoke
362                                  * record against a buffer_head which is
363                                  * not marked revoked --- that would
364                                  * risk missing a subsequent revoke
365                                  * cancel. */
366                                 J_ASSERT_BH(bh2, buffer_revoked(bh2));
367                         put_bh(bh2);
368                 }
369         }
370 #endif
371 
372         /* We really ought not ever to revoke twice in a row without
373            first having the revoke cancelled: it's illegal to free a
374            block twice without allocating it in between! */
375         if (bh) {
376                 if (!J_EXPECT_BH(bh, !buffer_revoked(bh),
377                                  "inconsistent data on disk")) {
378                         if (!bh_in)
379                                 brelse(bh);
380                         return -EIO;
381                 }
382                 set_buffer_revoked(bh);
383                 set_buffer_revokevalid(bh);
384                 if (bh_in) {
385                         BUFFER_TRACE(bh_in, "call jbd2_journal_forget");
386                         jbd2_journal_forget(handle, bh_in);
387                 } else {
388                         BUFFER_TRACE(bh, "call brelse");
389                         __brelse(bh);
390                 }
391         }
392 
393         jbd_debug(2, "insert revoke for block %llu, bh_in=%p\n",blocknr, bh_in);
394         err = insert_revoke_hash(journal, blocknr,
395                                 handle->h_transaction->t_tid);
396         BUFFER_TRACE(bh_in, "exit");
397         return err;
398 }
399 
400 /*
401  * Cancel an outstanding revoke.  For use only internally by the
402  * journaling code (called from jbd2_journal_get_write_access).
403  *
404  * We trust buffer_revoked() on the buffer if the buffer is already
405  * being journaled: if there is no revoke pending on the buffer, then we
406  * don't do anything here.
407  *
408  * This would break if it were possible for a buffer to be revoked and
409  * discarded, and then reallocated within the same transaction.  In such
410  * a case we would have lost the revoked bit, but when we arrived here
411  * the second time we would still have a pending revoke to cancel.  So,
412  * do not trust the Revoked bit on buffers unless RevokeValid is also
413  * set.
414  */
415 int jbd2_journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
416 {
417         struct jbd2_revoke_record_s *record;
418         journal_t *journal = handle->h_transaction->t_journal;
419         int need_cancel;
420         int did_revoke = 0;     /* akpm: debug */
421         struct buffer_head *bh = jh2bh(jh);
422 
423         jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
424 
425         /* Is the existing Revoke bit valid?  If so, we trust it, and
426          * only perform the full cancel if the revoke bit is set.  If
427          * not, we can't trust the revoke bit, and we need to do the
428          * full search for a revoke record. */
429         if (test_set_buffer_revokevalid(bh)) {
430                 need_cancel = test_clear_buffer_revoked(bh);
431         } else {
432                 need_cancel = 1;
433                 clear_buffer_revoked(bh);
434         }
435 
436         if (need_cancel) {
437                 record = find_revoke_record(journal, bh->b_blocknr);
438                 if (record) {
439                         jbd_debug(4, "cancelled existing revoke on "
440                                   "blocknr %llu\n", (unsigned long long)bh->b_blocknr);
441                         spin_lock(&journal->j_revoke_lock);
442                         list_del(&record->hash);
443                         spin_unlock(&journal->j_revoke_lock);
444                         kmem_cache_free(jbd2_revoke_record_cache, record);
445                         did_revoke = 1;
446                 }
447         }
448 
449 #ifdef JBD2_EXPENSIVE_CHECKING
450         /* There better not be one left behind by now! */
451         record = find_revoke_record(journal, bh->b_blocknr);
452         J_ASSERT_JH(jh, record == NULL);
453 #endif
454 
455         /* Finally, have we just cleared revoke on an unhashed
456          * buffer_head?  If so, we'd better make sure we clear the
457          * revoked status on any hashed alias too, otherwise the revoke
458          * state machine will get very upset later on. */
459         if (need_cancel) {
460                 struct buffer_head *bh2;
461                 bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
462                 if (bh2) {
463                         if (bh2 != bh)
464                                 clear_buffer_revoked(bh2);
465                         __brelse(bh2);
466                 }
467         }
468         return did_revoke;
469 }
470 
471 /*
472  * journal_clear_revoked_flag clears revoked flag of buffers in
473  * revoke table to reflect there is no revoked buffers in the next
474  * transaction which is going to be started.
475  */
476 void jbd2_clear_buffer_revoked_flags(journal_t *journal)
477 {
478         struct jbd2_revoke_table_s *revoke = journal->j_revoke;
479         int i = 0;
480 
481         for (i = 0; i < revoke->hash_size; i++) {
482                 struct list_head *hash_list;
483                 struct list_head *list_entry;
484                 hash_list = &revoke->hash_table[i];
485 
486                 list_for_each(list_entry, hash_list) {
487                         struct jbd2_revoke_record_s *record;
488                         struct buffer_head *bh;
489                         record = (struct jbd2_revoke_record_s *)list_entry;
490                         bh = __find_get_block(journal->j_fs_dev,
491                                               record->blocknr,
492                                               journal->j_blocksize);
493                         if (bh) {
494                                 clear_buffer_revoked(bh);
495                                 __brelse(bh);
496                         }
497                 }
498         }
499 }
500 
501 /* journal_switch_revoke table select j_revoke for next transaction
502  * we do not want to suspend any processing until all revokes are
503  * written -bzzz
504  */
505 void jbd2_journal_switch_revoke_table(journal_t *journal)
506 {
507         int i;
508 
509         if (journal->j_revoke == journal->j_revoke_table[0])
510                 journal->j_revoke = journal->j_revoke_table[1];
511         else
512                 journal->j_revoke = journal->j_revoke_table[0];
513 
514         for (i = 0; i < journal->j_revoke->hash_size; i++)
515                 INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
516 }
517 
518 /*
519  * Write revoke records to the journal for all entries in the current
520  * revoke hash, deleting the entries as we go.
521  */
522 void jbd2_journal_write_revoke_records(journal_t *journal,
523                                        transaction_t *transaction,
524                                        struct list_head *log_bufs,
525                                        int write_op)
526 {
527         struct buffer_head *descriptor;
528         struct jbd2_revoke_record_s *record;
529         struct jbd2_revoke_table_s *revoke;
530         struct list_head *hash_list;
531         int i, offset, count;
532 
533         descriptor = NULL;
534         offset = 0;
535         count = 0;
536 
537         /* select revoke table for committing transaction */
538         revoke = journal->j_revoke == journal->j_revoke_table[0] ?
539                 journal->j_revoke_table[1] : journal->j_revoke_table[0];
540 
541         for (i = 0; i < revoke->hash_size; i++) {
542                 hash_list = &revoke->hash_table[i];
543 
544                 while (!list_empty(hash_list)) {
545                         record = (struct jbd2_revoke_record_s *)
546                                 hash_list->next;
547                         write_one_revoke_record(journal, transaction, log_bufs,
548                                                 &descriptor, &offset,
549                                                 record, write_op);
550                         count++;
551                         list_del(&record->hash);
552                         kmem_cache_free(jbd2_revoke_record_cache, record);
553                 }
554         }
555         if (descriptor)
556                 flush_descriptor(journal, descriptor, offset, write_op);
557         jbd_debug(1, "Wrote %d revoke records\n", count);
558 }
559 
560 /*
561  * Write out one revoke record.  We need to create a new descriptor
562  * block if the old one is full or if we have not already created one.
563  */
564 
565 static void write_one_revoke_record(journal_t *journal,
566                                     transaction_t *transaction,
567                                     struct list_head *log_bufs,
568                                     struct buffer_head **descriptorp,
569                                     int *offsetp,
570                                     struct jbd2_revoke_record_s *record,
571                                     int write_op)
572 {
573         int csum_size = 0;
574         struct buffer_head *descriptor;
575         int sz, offset;
576         journal_header_t *header;
577 
578         /* If we are already aborting, this all becomes a noop.  We
579            still need to go round the loop in
580            jbd2_journal_write_revoke_records in order to free all of the
581            revoke records: only the IO to the journal is omitted. */
582         if (is_journal_aborted(journal))
583                 return;
584 
585         descriptor = *descriptorp;
586         offset = *offsetp;
587 
588         /* Do we need to leave space at the end for a checksum? */
589         if (jbd2_journal_has_csum_v2or3(journal))
590                 csum_size = sizeof(struct jbd2_journal_revoke_tail);
591 
592         if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
593                 sz = 8;
594         else
595                 sz = 4;
596 
597         /* Make sure we have a descriptor with space left for the record */
598         if (descriptor) {
599                 if (offset + sz > journal->j_blocksize - csum_size) {
600                         flush_descriptor(journal, descriptor, offset, write_op);
601                         descriptor = NULL;
602                 }
603         }
604 
605         if (!descriptor) {
606                 descriptor = jbd2_journal_get_descriptor_buffer(journal);
607                 if (!descriptor)
608                         return;
609                 header = (journal_header_t *)descriptor->b_data;
610                 header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
611                 header->h_blocktype = cpu_to_be32(JBD2_REVOKE_BLOCK);
612                 header->h_sequence  = cpu_to_be32(transaction->t_tid);
613 
614                 /* Record it so that we can wait for IO completion later */
615                 BUFFER_TRACE(descriptor, "file in log_bufs");
616                 jbd2_file_log_bh(log_bufs, descriptor);
617 
618                 offset = sizeof(jbd2_journal_revoke_header_t);
619                 *descriptorp = descriptor;
620         }
621 
622         if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
623                 * ((__be64 *)(&descriptor->b_data[offset])) =
624                         cpu_to_be64(record->blocknr);
625         else
626                 * ((__be32 *)(&descriptor->b_data[offset])) =
627                         cpu_to_be32(record->blocknr);
628         offset += sz;
629 
630         *offsetp = offset;
631 }
632 
633 static void jbd2_revoke_csum_set(journal_t *j, struct buffer_head *bh)
634 {
635         struct jbd2_journal_revoke_tail *tail;
636         __u32 csum;
637 
638         if (!jbd2_journal_has_csum_v2or3(j))
639                 return;
640 
641         tail = (struct jbd2_journal_revoke_tail *)(bh->b_data + j->j_blocksize -
642                         sizeof(struct jbd2_journal_revoke_tail));
643         tail->r_checksum = 0;
644         csum = jbd2_chksum(j, j->j_csum_seed, bh->b_data, j->j_blocksize);
645         tail->r_checksum = cpu_to_be32(csum);
646 }
647 
648 /*
649  * Flush a revoke descriptor out to the journal.  If we are aborting,
650  * this is a noop; otherwise we are generating a buffer which needs to
651  * be waited for during commit, so it has to go onto the appropriate
652  * journal buffer list.
653  */
654 
655 static void flush_descriptor(journal_t *journal,
656                              struct buffer_head *descriptor,
657                              int offset, int write_op)
658 {
659         jbd2_journal_revoke_header_t *header;
660 
661         if (is_journal_aborted(journal)) {
662                 put_bh(descriptor);
663                 return;
664         }
665 
666         header = (jbd2_journal_revoke_header_t *)descriptor->b_data;
667         header->r_count = cpu_to_be32(offset);
668         jbd2_revoke_csum_set(journal, descriptor);
669 
670         set_buffer_jwrite(descriptor);
671         BUFFER_TRACE(descriptor, "write");
672         set_buffer_dirty(descriptor);
673         write_dirty_buffer(descriptor, write_op);
674 }
675 #endif
676 
677 /*
678  * Revoke support for recovery.
679  *
680  * Recovery needs to be able to:
681  *
682  *  record all revoke records, including the tid of the latest instance
683  *  of each revoke in the journal
684  *
685  *  check whether a given block in a given transaction should be replayed
686  *  (ie. has not been revoked by a revoke record in that or a subsequent
687  *  transaction)
688  *
689  *  empty the revoke table after recovery.
690  */
691 
692 /*
693  * First, setting revoke records.  We create a new revoke record for
694  * every block ever revoked in the log as we scan it for recovery, and
695  * we update the existing records if we find multiple revokes for a
696  * single block.
697  */
698 
699 int jbd2_journal_set_revoke(journal_t *journal,
700                        unsigned long long blocknr,
701                        tid_t sequence)
702 {
703         struct jbd2_revoke_record_s *record;
704 
705         record = find_revoke_record(journal, blocknr);
706         if (record) {
707                 /* If we have multiple occurrences, only record the
708                  * latest sequence number in the hashed record */
709                 if (tid_gt(sequence, record->sequence))
710                         record->sequence = sequence;
711                 return 0;
712         }
713         return insert_revoke_hash(journal, blocknr, sequence);
714 }
715 
716 /*
717  * Test revoke records.  For a given block referenced in the log, has
718  * that block been revoked?  A revoke record with a given transaction
719  * sequence number revokes all blocks in that transaction and earlier
720  * ones, but later transactions still need replayed.
721  */
722 
723 int jbd2_journal_test_revoke(journal_t *journal,
724                         unsigned long long blocknr,
725                         tid_t sequence)
726 {
727         struct jbd2_revoke_record_s *record;
728 
729         record = find_revoke_record(journal, blocknr);
730         if (!record)
731                 return 0;
732         if (tid_gt(sequence, record->sequence))
733                 return 0;
734         return 1;
735 }
736 
737 /*
738  * Finally, once recovery is over, we need to clear the revoke table so
739  * that it can be reused by the running filesystem.
740  */
741 
742 void jbd2_journal_clear_revoke(journal_t *journal)
743 {
744         int i;
745         struct list_head *hash_list;
746         struct jbd2_revoke_record_s *record;
747         struct jbd2_revoke_table_s *revoke;
748 
749         revoke = journal->j_revoke;
750 
751         for (i = 0; i < revoke->hash_size; i++) {
752                 hash_list = &revoke->hash_table[i];
753                 while (!list_empty(hash_list)) {
754                         record = (struct jbd2_revoke_record_s*) hash_list->next;
755                         list_del(&record->hash);
756                         kmem_cache_free(jbd2_revoke_record_cache, record);
757                 }
758         }
759 }
760 

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