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Linux/fs/jbd2/revoke.c

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  1 // SPDX-License-Identifier: GPL-2.0+
  2 /*
  3  * linux/fs/jbd2/revoke.c
  4  *
  5  * Written by Stephen C. Tweedie <sct@redhat.com>, 2000
  6  *
  7  * Copyright 2000 Red Hat corp --- All Rights Reserved
  8  *
  9  * Journal revoke routines for the generic filesystem journaling code;
 10  * part of the ext2fs journaling system.
 11  *
 12  * Revoke is the mechanism used to prevent old log records for deleted
 13  * metadata from being replayed on top of newer data using the same
 14  * blocks.  The revoke mechanism is used in two separate places:
 15  *
 16  * + Commit: during commit we write the entire list of the current
 17  *   transaction's revoked blocks to the journal
 18  *
 19  * + Recovery: during recovery we record the transaction ID of all
 20  *   revoked blocks.  If there are multiple revoke records in the log
 21  *   for a single block, only the last one counts, and if there is a log
 22  *   entry for a block beyond the last revoke, then that log entry still
 23  *   gets replayed.
 24  *
 25  * We can get interactions between revokes and new log data within a
 26  * single transaction:
 27  *
 28  * Block is revoked and then journaled:
 29  *   The desired end result is the journaling of the new block, so we
 30  *   cancel the revoke before the transaction commits.
 31  *
 32  * Block is journaled and then revoked:
 33  *   The revoke must take precedence over the write of the block, so we
 34  *   need either to cancel the journal entry or to write the revoke
 35  *   later in the log than the log block.  In this case, we choose the
 36  *   latter: journaling a block cancels any revoke record for that block
 37  *   in the current transaction, so any revoke for that block in the
 38  *   transaction must have happened after the block was journaled and so
 39  *   the revoke must take precedence.
 40  *
 41  * Block is revoked and then written as data:
 42  *   The data write is allowed to succeed, but the revoke is _not_
 43  *   cancelled.  We still need to prevent old log records from
 44  *   overwriting the new data.  We don't even need to clear the revoke
 45  *   bit here.
 46  *
 47  * We cache revoke status of a buffer in the current transaction in b_states
 48  * bits.  As the name says, revokevalid flag indicates that the cached revoke
 49  * status of a buffer is valid and we can rely on the cached status.
 50  *
 51  * Revoke information on buffers is a tri-state value:
 52  *
 53  * RevokeValid clear:   no cached revoke status, need to look it up
 54  * RevokeValid set, Revoked clear:
 55  *                      buffer has not been revoked, and cancel_revoke
 56  *                      need do nothing.
 57  * RevokeValid set, Revoked set:
 58  *                      buffer has been revoked.
 59  *
 60  * Locking rules:
 61  * We keep two hash tables of revoke records. One hashtable belongs to the
 62  * running transaction (is pointed to by journal->j_revoke), the other one
 63  * belongs to the committing transaction. Accesses to the second hash table
 64  * happen only from the kjournald and no other thread touches this table.  Also
 65  * journal_switch_revoke_table() which switches which hashtable belongs to the
 66  * running and which to the committing transaction is called only from
 67  * kjournald. Therefore we need no locks when accessing the hashtable belonging
 68  * to the committing transaction.
 69  *
 70  * All users operating on the hash table belonging to the running transaction
 71  * have a handle to the transaction. Therefore they are safe from kjournald
 72  * switching hash tables under them. For operations on the lists of entries in
 73  * the hash table j_revoke_lock is used.
 74  *
 75  * Finally, also replay code uses the hash tables but at this moment no one else
 76  * can touch them (filesystem isn't mounted yet) and hence no locking is
 77  * needed.
 78  */
 79 
 80 #ifndef __KERNEL__
 81 #include "jfs_user.h"
 82 #else
 83 #include <linux/time.h>
 84 #include <linux/fs.h>
 85 #include <linux/jbd2.h>
 86 #include <linux/errno.h>
 87 #include <linux/slab.h>
 88 #include <linux/list.h>
 89 #include <linux/init.h>
 90 #include <linux/bio.h>
 91 #include <linux/log2.h>
 92 #include <linux/hash.h>
 93 #endif
 94 
 95 static struct kmem_cache *jbd2_revoke_record_cache;
 96 static struct kmem_cache *jbd2_revoke_table_cache;
 97 
 98 /* Each revoke record represents one single revoked block.  During
 99    journal replay, this involves recording the transaction ID of the
100    last transaction to revoke this block. */
101 
102 struct jbd2_revoke_record_s
103 {
104         struct list_head  hash;
105         tid_t             sequence;     /* Used for recovery only */
106         unsigned long long        blocknr;
107 };
108 
109 
110 /* The revoke table is just a simple hash table of revoke records. */
111 struct jbd2_revoke_table_s
112 {
113         /* It is conceivable that we might want a larger hash table
114          * for recovery.  Must be a power of two. */
115         int               hash_size;
116         int               hash_shift;
117         struct list_head *hash_table;
118 };
119 
120 
121 #ifdef __KERNEL__
122 static void write_one_revoke_record(transaction_t *,
123                                     struct list_head *,
124                                     struct buffer_head **, int *,
125                                     struct jbd2_revoke_record_s *);
126 static void flush_descriptor(journal_t *, struct buffer_head *, int);
127 #endif
128 
129 /* Utility functions to maintain the revoke table */
130 
131 static inline int hash(journal_t *journal, unsigned long long block)
132 {
133         return hash_64(block, journal->j_revoke->hash_shift);
134 }
135 
136 static int insert_revoke_hash(journal_t *journal, unsigned long long blocknr,
137                               tid_t seq)
138 {
139         struct list_head *hash_list;
140         struct jbd2_revoke_record_s *record;
141         gfp_t gfp_mask = GFP_NOFS;
142 
143         if (journal_oom_retry)
144                 gfp_mask |= __GFP_NOFAIL;
145         record = kmem_cache_alloc(jbd2_revoke_record_cache, gfp_mask);
146         if (!record)
147                 return -ENOMEM;
148 
149         record->sequence = seq;
150         record->blocknr = blocknr;
151         hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
152         spin_lock(&journal->j_revoke_lock);
153         list_add(&record->hash, hash_list);
154         spin_unlock(&journal->j_revoke_lock);
155         return 0;
156 }
157 
158 /* Find a revoke record in the journal's hash table. */
159 
160 static struct jbd2_revoke_record_s *find_revoke_record(journal_t *journal,
161                                                       unsigned long long blocknr)
162 {
163         struct list_head *hash_list;
164         struct jbd2_revoke_record_s *record;
165 
166         hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
167 
168         spin_lock(&journal->j_revoke_lock);
169         record = (struct jbd2_revoke_record_s *) hash_list->next;
170         while (&(record->hash) != hash_list) {
171                 if (record->blocknr == blocknr) {
172                         spin_unlock(&journal->j_revoke_lock);
173                         return record;
174                 }
175                 record = (struct jbd2_revoke_record_s *) record->hash.next;
176         }
177         spin_unlock(&journal->j_revoke_lock);
178         return NULL;
179 }
180 
181 void jbd2_journal_destroy_revoke_caches(void)
182 {
183         if (jbd2_revoke_record_cache) {
184                 kmem_cache_destroy(jbd2_revoke_record_cache);
185                 jbd2_revoke_record_cache = NULL;
186         }
187         if (jbd2_revoke_table_cache) {
188                 kmem_cache_destroy(jbd2_revoke_table_cache);
189                 jbd2_revoke_table_cache = NULL;
190         }
191 }
192 
193 int __init jbd2_journal_init_revoke_caches(void)
194 {
195         J_ASSERT(!jbd2_revoke_record_cache);
196         J_ASSERT(!jbd2_revoke_table_cache);
197 
198         jbd2_revoke_record_cache = KMEM_CACHE(jbd2_revoke_record_s,
199                                         SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY);
200         if (!jbd2_revoke_record_cache)
201                 goto record_cache_failure;
202 
203         jbd2_revoke_table_cache = KMEM_CACHE(jbd2_revoke_table_s,
204                                              SLAB_TEMPORARY);
205         if (!jbd2_revoke_table_cache)
206                 goto table_cache_failure;
207         return 0;
208 table_cache_failure:
209         jbd2_journal_destroy_revoke_caches();
210 record_cache_failure:
211                 return -ENOMEM;
212 }
213 
214 static struct jbd2_revoke_table_s *jbd2_journal_init_revoke_table(int hash_size)
215 {
216         int shift = 0;
217         int tmp = hash_size;
218         struct jbd2_revoke_table_s *table;
219 
220         table = kmem_cache_alloc(jbd2_revoke_table_cache, GFP_KERNEL);
221         if (!table)
222                 goto out;
223 
224         while((tmp >>= 1UL) != 0UL)
225                 shift++;
226 
227         table->hash_size = hash_size;
228         table->hash_shift = shift;
229         table->hash_table =
230                 kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
231         if (!table->hash_table) {
232                 kmem_cache_free(jbd2_revoke_table_cache, table);
233                 table = NULL;
234                 goto out;
235         }
236 
237         for (tmp = 0; tmp < hash_size; tmp++)
238                 INIT_LIST_HEAD(&table->hash_table[tmp]);
239 
240 out:
241         return table;
242 }
243 
244 static void jbd2_journal_destroy_revoke_table(struct jbd2_revoke_table_s *table)
245 {
246         int i;
247         struct list_head *hash_list;
248 
249         for (i = 0; i < table->hash_size; i++) {
250                 hash_list = &table->hash_table[i];
251                 J_ASSERT(list_empty(hash_list));
252         }
253 
254         kfree(table->hash_table);
255         kmem_cache_free(jbd2_revoke_table_cache, table);
256 }
257 
258 /* Initialise the revoke table for a given journal to a given size. */
259 int jbd2_journal_init_revoke(journal_t *journal, int hash_size)
260 {
261         J_ASSERT(journal->j_revoke_table[0] == NULL);
262         J_ASSERT(is_power_of_2(hash_size));
263 
264         journal->j_revoke_table[0] = jbd2_journal_init_revoke_table(hash_size);
265         if (!journal->j_revoke_table[0])
266                 goto fail0;
267 
268         journal->j_revoke_table[1] = jbd2_journal_init_revoke_table(hash_size);
269         if (!journal->j_revoke_table[1])
270                 goto fail1;
271 
272         journal->j_revoke = journal->j_revoke_table[1];
273 
274         spin_lock_init(&journal->j_revoke_lock);
275 
276         return 0;
277 
278 fail1:
279         jbd2_journal_destroy_revoke_table(journal->j_revoke_table[0]);
280         journal->j_revoke_table[0] = NULL;
281 fail0:
282         return -ENOMEM;
283 }
284 
285 /* Destroy a journal's revoke table.  The table must already be empty! */
286 void jbd2_journal_destroy_revoke(journal_t *journal)
287 {
288         journal->j_revoke = NULL;
289         if (journal->j_revoke_table[0])
290                 jbd2_journal_destroy_revoke_table(journal->j_revoke_table[0]);
291         if (journal->j_revoke_table[1])
292                 jbd2_journal_destroy_revoke_table(journal->j_revoke_table[1]);
293 }
294 
295 
296 #ifdef __KERNEL__
297 
298 /*
299  * jbd2_journal_revoke: revoke a given buffer_head from the journal.  This
300  * prevents the block from being replayed during recovery if we take a
301  * crash after this current transaction commits.  Any subsequent
302  * metadata writes of the buffer in this transaction cancel the
303  * revoke.
304  *
305  * Note that this call may block --- it is up to the caller to make
306  * sure that there are no further calls to journal_write_metadata
307  * before the revoke is complete.  In ext3, this implies calling the
308  * revoke before clearing the block bitmap when we are deleting
309  * metadata.
310  *
311  * Revoke performs a jbd2_journal_forget on any buffer_head passed in as a
312  * parameter, but does _not_ forget the buffer_head if the bh was only
313  * found implicitly.
314  *
315  * bh_in may not be a journalled buffer - it may have come off
316  * the hash tables without an attached journal_head.
317  *
318  * If bh_in is non-zero, jbd2_journal_revoke() will decrement its b_count
319  * by one.
320  */
321 
322 int jbd2_journal_revoke(handle_t *handle, unsigned long long blocknr,
323                    struct buffer_head *bh_in)
324 {
325         struct buffer_head *bh = NULL;
326         journal_t *journal;
327         struct block_device *bdev;
328         int err;
329 
330         might_sleep();
331         if (bh_in)
332                 BUFFER_TRACE(bh_in, "enter");
333 
334         journal = handle->h_transaction->t_journal;
335         if (!jbd2_journal_set_features(journal, 0, 0, JBD2_FEATURE_INCOMPAT_REVOKE)){
336                 J_ASSERT (!"Cannot set revoke feature!");
337                 return -EINVAL;
338         }
339 
340         bdev = journal->j_fs_dev;
341         bh = bh_in;
342 
343         if (!bh) {
344                 bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
345                 if (bh)
346                         BUFFER_TRACE(bh, "found on hash");
347         }
348 #ifdef JBD2_EXPENSIVE_CHECKING
349         else {
350                 struct buffer_head *bh2;
351 
352                 /* If there is a different buffer_head lying around in
353                  * memory anywhere... */
354                 bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
355                 if (bh2) {
356                         /* ... and it has RevokeValid status... */
357                         if (bh2 != bh && buffer_revokevalid(bh2))
358                                 /* ...then it better be revoked too,
359                                  * since it's illegal to create a revoke
360                                  * record against a buffer_head which is
361                                  * not marked revoked --- that would
362                                  * risk missing a subsequent revoke
363                                  * cancel. */
364                                 J_ASSERT_BH(bh2, buffer_revoked(bh2));
365                         put_bh(bh2);
366                 }
367         }
368 #endif
369 
370         /* We really ought not ever to revoke twice in a row without
371            first having the revoke cancelled: it's illegal to free a
372            block twice without allocating it in between! */
373         if (bh) {
374                 if (!J_EXPECT_BH(bh, !buffer_revoked(bh),
375                                  "inconsistent data on disk")) {
376                         if (!bh_in)
377                                 brelse(bh);
378                         return -EIO;
379                 }
380                 set_buffer_revoked(bh);
381                 set_buffer_revokevalid(bh);
382                 if (bh_in) {
383                         BUFFER_TRACE(bh_in, "call jbd2_journal_forget");
384                         jbd2_journal_forget(handle, bh_in);
385                 } else {
386                         BUFFER_TRACE(bh, "call brelse");
387                         __brelse(bh);
388                 }
389         }
390 
391         jbd_debug(2, "insert revoke for block %llu, bh_in=%p\n",blocknr, bh_in);
392         err = insert_revoke_hash(journal, blocknr,
393                                 handle->h_transaction->t_tid);
394         BUFFER_TRACE(bh_in, "exit");
395         return err;
396 }
397 
398 /*
399  * Cancel an outstanding revoke.  For use only internally by the
400  * journaling code (called from jbd2_journal_get_write_access).
401  *
402  * We trust buffer_revoked() on the buffer if the buffer is already
403  * being journaled: if there is no revoke pending on the buffer, then we
404  * don't do anything here.
405  *
406  * This would break if it were possible for a buffer to be revoked and
407  * discarded, and then reallocated within the same transaction.  In such
408  * a case we would have lost the revoked bit, but when we arrived here
409  * the second time we would still have a pending revoke to cancel.  So,
410  * do not trust the Revoked bit on buffers unless RevokeValid is also
411  * set.
412  */
413 int jbd2_journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
414 {
415         struct jbd2_revoke_record_s *record;
416         journal_t *journal = handle->h_transaction->t_journal;
417         int need_cancel;
418         int did_revoke = 0;     /* akpm: debug */
419         struct buffer_head *bh = jh2bh(jh);
420 
421         jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
422 
423         /* Is the existing Revoke bit valid?  If so, we trust it, and
424          * only perform the full cancel if the revoke bit is set.  If
425          * not, we can't trust the revoke bit, and we need to do the
426          * full search for a revoke record. */
427         if (test_set_buffer_revokevalid(bh)) {
428                 need_cancel = test_clear_buffer_revoked(bh);
429         } else {
430                 need_cancel = 1;
431                 clear_buffer_revoked(bh);
432         }
433 
434         if (need_cancel) {
435                 record = find_revoke_record(journal, bh->b_blocknr);
436                 if (record) {
437                         jbd_debug(4, "cancelled existing revoke on "
438                                   "blocknr %llu\n", (unsigned long long)bh->b_blocknr);
439                         spin_lock(&journal->j_revoke_lock);
440                         list_del(&record->hash);
441                         spin_unlock(&journal->j_revoke_lock);
442                         kmem_cache_free(jbd2_revoke_record_cache, record);
443                         did_revoke = 1;
444                 }
445         }
446 
447 #ifdef JBD2_EXPENSIVE_CHECKING
448         /* There better not be one left behind by now! */
449         record = find_revoke_record(journal, bh->b_blocknr);
450         J_ASSERT_JH(jh, record == NULL);
451 #endif
452 
453         /* Finally, have we just cleared revoke on an unhashed
454          * buffer_head?  If so, we'd better make sure we clear the
455          * revoked status on any hashed alias too, otherwise the revoke
456          * state machine will get very upset later on. */
457         if (need_cancel) {
458                 struct buffer_head *bh2;
459                 bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
460                 if (bh2) {
461                         if (bh2 != bh)
462                                 clear_buffer_revoked(bh2);
463                         __brelse(bh2);
464                 }
465         }
466         return did_revoke;
467 }
468 
469 /*
470  * journal_clear_revoked_flag clears revoked flag of buffers in
471  * revoke table to reflect there is no revoked buffers in the next
472  * transaction which is going to be started.
473  */
474 void jbd2_clear_buffer_revoked_flags(journal_t *journal)
475 {
476         struct jbd2_revoke_table_s *revoke = journal->j_revoke;
477         int i = 0;
478 
479         for (i = 0; i < revoke->hash_size; i++) {
480                 struct list_head *hash_list;
481                 struct list_head *list_entry;
482                 hash_list = &revoke->hash_table[i];
483 
484                 list_for_each(list_entry, hash_list) {
485                         struct jbd2_revoke_record_s *record;
486                         struct buffer_head *bh;
487                         record = (struct jbd2_revoke_record_s *)list_entry;
488                         bh = __find_get_block(journal->j_fs_dev,
489                                               record->blocknr,
490                                               journal->j_blocksize);
491                         if (bh) {
492                                 clear_buffer_revoked(bh);
493                                 __brelse(bh);
494                         }
495                 }
496         }
497 }
498 
499 /* journal_switch_revoke table select j_revoke for next transaction
500  * we do not want to suspend any processing until all revokes are
501  * written -bzzz
502  */
503 void jbd2_journal_switch_revoke_table(journal_t *journal)
504 {
505         int i;
506 
507         if (journal->j_revoke == journal->j_revoke_table[0])
508                 journal->j_revoke = journal->j_revoke_table[1];
509         else
510                 journal->j_revoke = journal->j_revoke_table[0];
511 
512         for (i = 0; i < journal->j_revoke->hash_size; i++)
513                 INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
514 }
515 
516 /*
517  * Write revoke records to the journal for all entries in the current
518  * revoke hash, deleting the entries as we go.
519  */
520 void jbd2_journal_write_revoke_records(transaction_t *transaction,
521                                        struct list_head *log_bufs)
522 {
523         journal_t *journal = transaction->t_journal;
524         struct buffer_head *descriptor;
525         struct jbd2_revoke_record_s *record;
526         struct jbd2_revoke_table_s *revoke;
527         struct list_head *hash_list;
528         int i, offset, count;
529 
530         descriptor = NULL;
531         offset = 0;
532         count = 0;
533 
534         /* select revoke table for committing transaction */
535         revoke = journal->j_revoke == journal->j_revoke_table[0] ?
536                 journal->j_revoke_table[1] : journal->j_revoke_table[0];
537 
538         for (i = 0; i < revoke->hash_size; i++) {
539                 hash_list = &revoke->hash_table[i];
540 
541                 while (!list_empty(hash_list)) {
542                         record = (struct jbd2_revoke_record_s *)
543                                 hash_list->next;
544                         write_one_revoke_record(transaction, log_bufs,
545                                                 &descriptor, &offset, record);
546                         count++;
547                         list_del(&record->hash);
548                         kmem_cache_free(jbd2_revoke_record_cache, record);
549                 }
550         }
551         if (descriptor)
552                 flush_descriptor(journal, descriptor, offset);
553         jbd_debug(1, "Wrote %d revoke records\n", count);
554 }
555 
556 /*
557  * Write out one revoke record.  We need to create a new descriptor
558  * block if the old one is full or if we have not already created one.
559  */
560 
561 static void write_one_revoke_record(transaction_t *transaction,
562                                     struct list_head *log_bufs,
563                                     struct buffer_head **descriptorp,
564                                     int *offsetp,
565                                     struct jbd2_revoke_record_s *record)
566 {
567         journal_t *journal = transaction->t_journal;
568         int csum_size = 0;
569         struct buffer_head *descriptor;
570         int sz, offset;
571 
572         /* If we are already aborting, this all becomes a noop.  We
573            still need to go round the loop in
574            jbd2_journal_write_revoke_records in order to free all of the
575            revoke records: only the IO to the journal is omitted. */
576         if (is_journal_aborted(journal))
577                 return;
578 
579         descriptor = *descriptorp;
580         offset = *offsetp;
581 
582         /* Do we need to leave space at the end for a checksum? */
583         if (jbd2_journal_has_csum_v2or3(journal))
584                 csum_size = sizeof(struct jbd2_journal_block_tail);
585 
586         if (jbd2_has_feature_64bit(journal))
587                 sz = 8;
588         else
589                 sz = 4;
590 
591         /* Make sure we have a descriptor with space left for the record */
592         if (descriptor) {
593                 if (offset + sz > journal->j_blocksize - csum_size) {
594                         flush_descriptor(journal, descriptor, offset);
595                         descriptor = NULL;
596                 }
597         }
598 
599         if (!descriptor) {
600                 descriptor = jbd2_journal_get_descriptor_buffer(transaction,
601                                                         JBD2_REVOKE_BLOCK);
602                 if (!descriptor)
603                         return;
604 
605                 /* Record it so that we can wait for IO completion later */
606                 BUFFER_TRACE(descriptor, "file in log_bufs");
607                 jbd2_file_log_bh(log_bufs, descriptor);
608 
609                 offset = sizeof(jbd2_journal_revoke_header_t);
610                 *descriptorp = descriptor;
611         }
612 
613         if (jbd2_has_feature_64bit(journal))
614                 * ((__be64 *)(&descriptor->b_data[offset])) =
615                         cpu_to_be64(record->blocknr);
616         else
617                 * ((__be32 *)(&descriptor->b_data[offset])) =
618                         cpu_to_be32(record->blocknr);
619         offset += sz;
620 
621         *offsetp = offset;
622 }
623 
624 /*
625  * Flush a revoke descriptor out to the journal.  If we are aborting,
626  * this is a noop; otherwise we are generating a buffer which needs to
627  * be waited for during commit, so it has to go onto the appropriate
628  * journal buffer list.
629  */
630 
631 static void flush_descriptor(journal_t *journal,
632                              struct buffer_head *descriptor,
633                              int offset)
634 {
635         jbd2_journal_revoke_header_t *header;
636 
637         if (is_journal_aborted(journal)) {
638                 put_bh(descriptor);
639                 return;
640         }
641 
642         header = (jbd2_journal_revoke_header_t *)descriptor->b_data;
643         header->r_count = cpu_to_be32(offset);
644         jbd2_descriptor_block_csum_set(journal, descriptor);
645 
646         set_buffer_jwrite(descriptor);
647         BUFFER_TRACE(descriptor, "write");
648         set_buffer_dirty(descriptor);
649         write_dirty_buffer(descriptor, REQ_SYNC);
650 }
651 #endif
652 
653 /*
654  * Revoke support for recovery.
655  *
656  * Recovery needs to be able to:
657  *
658  *  record all revoke records, including the tid of the latest instance
659  *  of each revoke in the journal
660  *
661  *  check whether a given block in a given transaction should be replayed
662  *  (ie. has not been revoked by a revoke record in that or a subsequent
663  *  transaction)
664  *
665  *  empty the revoke table after recovery.
666  */
667 
668 /*
669  * First, setting revoke records.  We create a new revoke record for
670  * every block ever revoked in the log as we scan it for recovery, and
671  * we update the existing records if we find multiple revokes for a
672  * single block.
673  */
674 
675 int jbd2_journal_set_revoke(journal_t *journal,
676                        unsigned long long blocknr,
677                        tid_t sequence)
678 {
679         struct jbd2_revoke_record_s *record;
680 
681         record = find_revoke_record(journal, blocknr);
682         if (record) {
683                 /* If we have multiple occurrences, only record the
684                  * latest sequence number in the hashed record */
685                 if (tid_gt(sequence, record->sequence))
686                         record->sequence = sequence;
687                 return 0;
688         }
689         return insert_revoke_hash(journal, blocknr, sequence);
690 }
691 
692 /*
693  * Test revoke records.  For a given block referenced in the log, has
694  * that block been revoked?  A revoke record with a given transaction
695  * sequence number revokes all blocks in that transaction and earlier
696  * ones, but later transactions still need replayed.
697  */
698 
699 int jbd2_journal_test_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                 return 0;
708         if (tid_gt(sequence, record->sequence))
709                 return 0;
710         return 1;
711 }
712 
713 /*
714  * Finally, once recovery is over, we need to clear the revoke table so
715  * that it can be reused by the running filesystem.
716  */
717 
718 void jbd2_journal_clear_revoke(journal_t *journal)
719 {
720         int i;
721         struct list_head *hash_list;
722         struct jbd2_revoke_record_s *record;
723         struct jbd2_revoke_table_s *revoke;
724 
725         revoke = journal->j_revoke;
726 
727         for (i = 0; i < revoke->hash_size; i++) {
728                 hash_list = &revoke->hash_table[i];
729                 while (!list_empty(hash_list)) {
730                         record = (struct jbd2_revoke_record_s*) hash_list->next;
731                         list_del(&record->hash);
732                         kmem_cache_free(jbd2_revoke_record_cache, record);
733                 }
734         }
735 }
736 

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