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      1 /*
      2  * linux/fs/jbd2/revoke.c
      3  *
      4  * Written by Stephen C. Tweedie <sct (at) 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 #endif
     96 
     97 static lkmem_cache_t *jbd2_revoke_record_cache;
     98 static lkmem_cache_t *jbd2_revoke_table_cache;
     99 
    100 /* Each revoke record represents one single revoked block.  During
    101    journal replay, this involves recording the transaction ID of the
    102    last transaction to revoke this block. */
    103 
    104 struct jbd2_revoke_record_s
    105 {
    106 	struct list_head  hash;
    107 	tid_t		  sequence;	/* Used for recovery only */
    108 	unsigned long long	  blocknr;
    109 };
    110 
    111 
    112 /* The revoke table is just a simple hash table of revoke records. */
    113 struct jbd2_revoke_table_s
    114 {
    115 	/* It is conceivable that we might want a larger hash table
    116 	 * for recovery.  Must be a power of two. */
    117 	int		  hash_size;
    118 	int		  hash_shift;
    119 	struct list_head *hash_table;
    120 };
    121 
    122 
    123 #ifdef __KERNEL__
    124 static void write_one_revoke_record(journal_t *, transaction_t *,
    125 				    struct list_head *,
    126 				    struct buffer_head **, int *,
    127 				    struct jbd2_revoke_record_s *, int);
    128 static void flush_descriptor(journal_t *, struct buffer_head *, int, int);
    129 #endif
    130 
    131 /* Utility functions to maintain the revoke table */
    132 
    133 /* Borrowed from buffer.c: this is a tried and tested block hash function */
    134 static inline int hash(journal_t *journal, unsigned long long block)
    135 {
    136 	struct jbd2_revoke_table_s *table = journal->j_revoke;
    137 	int hash_shift = table->hash_shift;
    138 	int hash = (int)block ^ (int)((block >> 31) >> 1);
    139 
    140 	return ((hash << (hash_shift - 6)) ^
    141 		(hash >> 13) ^
    142 		(hash << (hash_shift - 12))) & (table->hash_size - 1);
    143 }
    144 
    145 static int insert_revoke_hash(journal_t *journal, unsigned long long blocknr,
    146 			      tid_t seq)
    147 {
    148 	struct list_head *hash_list;
    149 	struct jbd2_revoke_record_s *record;
    150 
    151 repeat:
    152 	record = kmem_cache_alloc(jbd2_revoke_record_cache, GFP_NOFS);
    153 	if (!record)
    154 		goto oom;
    155 
    156 	record->sequence = seq;
    157 	record->blocknr = blocknr;
    158 	hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
    159 	spin_lock(&journal->j_revoke_lock);
    160 	list_add(&record->hash, hash_list);
    161 	spin_unlock(&journal->j_revoke_lock);
    162 	return 0;
    163 
    164 oom:
    165 	if (!journal_oom_retry)
    166 		return -ENOMEM;
    167 	jbd_debug(1, "ENOMEM in %s, retrying\n", __func__);
    168 	yield();
    169 	goto repeat;
    170 }
    171 
    172 /* Find a revoke record in the journal's hash table. */
    173 
    174 static struct jbd2_revoke_record_s *find_revoke_record(journal_t *journal,
    175 						      unsigned long long blocknr)
    176 {
    177 	struct list_head *hash_list;
    178 	struct jbd2_revoke_record_s *record;
    179 
    180 	hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
    181 
    182 	spin_lock(&journal->j_revoke_lock);
    183 	record = (struct jbd2_revoke_record_s *) hash_list->next;
    184 	while (&(record->hash) != hash_list) {
    185 		if (record->blocknr == blocknr) {
    186 			spin_unlock(&journal->j_revoke_lock);
    187 			return record;
    188 		}
    189 		record = (struct jbd2_revoke_record_s *) record->hash.next;
    190 	}
    191 	spin_unlock(&journal->j_revoke_lock);
    192 	return NULL;
    193 }
    194 
    195 void journal_destroy_revoke_caches(void)
    196 {
    197 	if (jbd2_revoke_record_cache) {
    198 		kmem_cache_destroy(jbd2_revoke_record_cache);
    199 		jbd2_revoke_record_cache = NULL;
    200 	}
    201 	if (jbd2_revoke_table_cache) {
    202 		kmem_cache_destroy(jbd2_revoke_table_cache);
    203 		jbd2_revoke_table_cache = NULL;
    204 	}
    205 }
    206 
    207 int __init journal_init_revoke_caches(void)
    208 {
    209 	J_ASSERT(!jbd2_revoke_record_cache);
    210 	J_ASSERT(!jbd2_revoke_table_cache);
    211 
    212 	jbd2_revoke_record_cache = KMEM_CACHE(jbd2_revoke_record_s,
    213 					SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY);
    214 	if (!jbd2_revoke_record_cache)
    215 		goto record_cache_failure;
    216 
    217 	jbd2_revoke_table_cache = KMEM_CACHE(jbd2_revoke_table_s,
    218 					     SLAB_TEMPORARY);
    219 	if (!jbd2_revoke_table_cache)
    220 		goto table_cache_failure;
    221 	return 0;
    222 table_cache_failure:
    223 	journal_destroy_revoke_caches();
    224 record_cache_failure:
    225 		return -ENOMEM;
    226 }
    227 
    228 static struct jbd2_revoke_table_s *journal_init_revoke_table(int hash_size)
    229 {
    230 	int shift = 0;
    231 	int tmp = hash_size;
    232 	struct jbd2_revoke_table_s *table;
    233 
    234 	table = kmem_cache_alloc(jbd2_revoke_table_cache, GFP_KERNEL);
    235 	if (!table)
    236 		goto out;
    237 
    238 	while((tmp >>= 1UL) != 0UL)
    239 		shift++;
    240 
    241 	table->hash_size = hash_size;
    242 	table->hash_shift = shift;
    243 	table->hash_table =
    244 		kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
    245 	if (!table->hash_table) {
    246 		kmem_cache_free(jbd2_revoke_table_cache, table);
    247 		table = NULL;
    248 		goto out;
    249 	}
    250 
    251 	for (tmp = 0; tmp < hash_size; tmp++)
    252 		INIT_LIST_HEAD(&table->hash_table[tmp]);
    253 
    254 out:
    255 	return table;
    256 }
    257 
    258 static void journal_destroy_revoke_table(struct jbd2_revoke_table_s *table)
    259 {
    260 	int i;
    261 	struct list_head *hash_list;
    262 
    263 	for (i = 0; i < table->hash_size; i++) {
    264 		hash_list = &table->hash_table[i];
    265 		J_ASSERT(list_empty(hash_list));
    266 	}
    267 
    268 	kfree(table->hash_table);
    269 	kmem_cache_free(jbd2_revoke_table_cache, table);
    270 }
    271 
    272 /* Initialise the revoke table for a given journal to a given size. */
    273 int journal_init_revoke(journal_t *journal, int hash_size)
    274 {
    275 	J_ASSERT(journal->j_revoke_table[0] == NULL);
    276 	J_ASSERT(is_power_of_2(hash_size));
    277 
    278 	journal->j_revoke_table[0] = journal_init_revoke_table(hash_size);
    279 	if (!journal->j_revoke_table[0])
    280 		goto fail0;
    281 
    282 	journal->j_revoke_table[1] = journal_init_revoke_table(hash_size);
    283 	if (!journal->j_revoke_table[1])
    284 		goto fail1;
    285 
    286 	journal->j_revoke = journal->j_revoke_table[1];
    287 
    288 	spin_lock_init(&journal->j_revoke_lock);
    289 
    290 	return 0;
    291 
    292 fail1:
    293 	journal_destroy_revoke_table(journal->j_revoke_table[0]);
    294 fail0:
    295 	return -ENOMEM;
    296 }
    297 
    298 /* Destroy a journal's revoke table.  The table must already be empty! */
    299 void journal_destroy_revoke(journal_t *journal)
    300 {
    301 	journal->j_revoke = NULL;
    302 	if (journal->j_revoke_table[0])
    303 		journal_destroy_revoke_table(journal->j_revoke_table[0]);
    304 	if (journal->j_revoke_table[1])
    305 		journal_destroy_revoke_table(journal->j_revoke_table[1]);
    306 }
    307 
    308 
    309 #ifdef __KERNEL__
    310 
    311 /*
    312  * journal_revoke: revoke a given buffer_head from the journal.  This
    313  * prevents the block from being replayed during recovery if we take a
    314  * crash after this current transaction commits.  Any subsequent
    315  * metadata writes of the buffer in this transaction cancel the
    316  * revoke.
    317  *
    318  * Note that this call may block --- it is up to the caller to make
    319  * sure that there are no further calls to journal_write_metadata
    320  * before the revoke is complete.  In ext3, this implies calling the
    321  * revoke before clearing the block bitmap when we are deleting
    322  * metadata.
    323  *
    324  * Revoke performs a journal_forget on any buffer_head passed in as a
    325  * parameter, but does _not_ forget the buffer_head if the bh was only
    326  * found implicitly.
    327  *
    328  * bh_in may not be a journalled buffer - it may have come off
    329  * the hash tables without an attached journal_head.
    330  *
    331  * If bh_in is non-zero, journal_revoke() will decrement its b_count
    332  * by one.
    333  */
    334 
    335 int journal_revoke(handle_t *handle, unsigned long long blocknr,
    336 		   struct buffer_head *bh_in)
    337 {
    338 	struct buffer_head *bh = NULL;
    339 	journal_t *journal;
    340 	struct block_device *bdev;
    341 	int err;
    342 
    343 	might_sleep();
    344 	if (bh_in)
    345 		BUFFER_TRACE(bh_in, "enter");
    346 
    347 	journal = handle->h_transaction->t_journal;
    348 	if (!journal_set_features(journal, 0, 0, JFS_FEATURE_INCOMPAT_REVOKE)){
    349 		J_ASSERT (!"Cannot set revoke feature!");
    350 		return -EINVAL;
    351 	}
    352 
    353 	bdev = journal->j_fs_dev;
    354 	bh = bh_in;
    355 
    356 	if (!bh) {
    357 		bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
    358 		if (bh)
    359 			BUFFER_TRACE(bh, "found on hash");
    360 	}
    361 #ifdef JFS_EXPENSIVE_CHECKING
    362 	else {
    363 		struct buffer_head *bh2;
    364 
    365 		/* If there is a different buffer_head lying around in
    366 		 * memory anywhere... */
    367 		bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
    368 		if (bh2) {
    369 			/* ... and it has RevokeValid status... */
    370 			if (bh2 != bh && buffer_revokevalid(bh2))
    371 				/* ...then it better be revoked too,
    372 				 * since it's illegal to create a revoke
    373 				 * record against a buffer_head which is
    374 				 * not marked revoked --- that would
    375 				 * risk missing a subsequent revoke
    376 				 * cancel. */
    377 				J_ASSERT_BH(bh2, buffer_revoked(bh2));
    378 			put_bh(bh2);
    379 		}
    380 	}
    381 #endif
    382 
    383 	/* We really ought not ever to revoke twice in a row without
    384            first having the revoke cancelled: it's illegal to free a
    385            block twice without allocating it in between! */
    386 	if (bh) {
    387 		if (!J_EXPECT_BH(bh, !buffer_revoked(bh),
    388 				 "inconsistent data on disk")) {
    389 			if (!bh_in)
    390 				brelse(bh);
    391 			return -EIO;
    392 		}
    393 		set_buffer_revoked(bh);
    394 		set_buffer_revokevalid(bh);
    395 		if (bh_in) {
    396 			BUFFER_TRACE(bh_in, "call journal_forget");
    397 			journal_forget(handle, bh_in);
    398 		} else {
    399 			BUFFER_TRACE(bh, "call brelse");
    400 			__brelse(bh);
    401 		}
    402 	}
    403 
    404 	jbd_debug(2, "insert revoke for block %llu, bh_in=%p\n",blocknr, bh_in);
    405 	err = insert_revoke_hash(journal, blocknr,
    406 				handle->h_transaction->t_tid);
    407 	BUFFER_TRACE(bh_in, "exit");
    408 	return err;
    409 }
    410 
    411 /*
    412  * Cancel an outstanding revoke.  For use only internally by the
    413  * journaling code (called from journal_get_write_access).
    414  *
    415  * We trust buffer_revoked() on the buffer if the buffer is already
    416  * being journaled: if there is no revoke pending on the buffer, then we
    417  * don't do anything here.
    418  *
    419  * This would break if it were possible for a buffer to be revoked and
    420  * discarded, and then reallocated within the same transaction.  In such
    421  * a case we would have lost the revoked bit, but when we arrived here
    422  * the second time we would still have a pending revoke to cancel.  So,
    423  * do not trust the Revoked bit on buffers unless RevokeValid is also
    424  * set.
    425  */
    426 int journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
    427 {
    428 	struct jbd2_revoke_record_s *record;
    429 	journal_t *journal = handle->h_transaction->t_journal;
    430 	int need_cancel;
    431 	int did_revoke = 0;	/* akpm: debug */
    432 	struct buffer_head *bh = jh2bh(jh);
    433 
    434 	jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
    435 
    436 	/* Is the existing Revoke bit valid?  If so, we trust it, and
    437 	 * only perform the full cancel if the revoke bit is set.  If
    438 	 * not, we can't trust the revoke bit, and we need to do the
    439 	 * full search for a revoke record. */
    440 	if (test_set_buffer_revokevalid(bh)) {
    441 		need_cancel = test_clear_buffer_revoked(bh);
    442 	} else {
    443 		need_cancel = 1;
    444 		clear_buffer_revoked(bh);
    445 	}
    446 
    447 	if (need_cancel) {
    448 		record = find_revoke_record(journal, bh->b_blocknr);
    449 		if (record) {
    450 			jbd_debug(4, "cancelled existing revoke on "
    451 				  "blocknr %llu\n", (unsigned long long)bh->b_blocknr);
    452 			spin_lock(&journal->j_revoke_lock);
    453 			list_del(&record->hash);
    454 			spin_unlock(&journal->j_revoke_lock);
    455 			kmem_cache_free(jbd2_revoke_record_cache, record);
    456 			did_revoke = 1;
    457 		}
    458 	}
    459 
    460 #ifdef JFS_EXPENSIVE_CHECKING
    461 	/* There better not be one left behind by now! */
    462 	record = find_revoke_record(journal, bh->b_blocknr);
    463 	J_ASSERT_JH(jh, record == NULL);
    464 #endif
    465 
    466 	/* Finally, have we just cleared revoke on an unhashed
    467 	 * buffer_head?  If so, we'd better make sure we clear the
    468 	 * revoked status on any hashed alias too, otherwise the revoke
    469 	 * state machine will get very upset later on. */
    470 	if (need_cancel) {
    471 		struct buffer_head *bh2;
    472 		bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
    473 		if (bh2) {
    474 			if (bh2 != bh)
    475 				clear_buffer_revoked(bh2);
    476 			__brelse(bh2);
    477 		}
    478 	}
    479 	return did_revoke;
    480 }
    481 
    482 /*
    483  * journal_clear_revoked_flag clears revoked flag of buffers in
    484  * revoke table to reflect there is no revoked buffers in the next
    485  * transaction which is going to be started.
    486  */
    487 void jbd2_clear_buffer_revoked_flags(journal_t *journal)
    488 {
    489 	struct jbd2_revoke_table_s *revoke = journal->j_revoke;
    490 	int i = 0;
    491 
    492 	for (i = 0; i < revoke->hash_size; i++) {
    493 		struct list_head *hash_list;
    494 		struct list_head *list_entry;
    495 		hash_list = &revoke->hash_table[i];
    496 
    497 		list_for_each(list_entry, hash_list) {
    498 			struct jbd2_revoke_record_s *record;
    499 			struct buffer_head *bh;
    500 			record = (struct jbd2_revoke_record_s *)list_entry;
    501 			bh = __find_get_block(journal->j_fs_dev,
    502 					      record->blocknr,
    503 					      journal->j_blocksize);
    504 			if (bh) {
    505 				clear_buffer_revoked(bh);
    506 				__brelse(bh);
    507 			}
    508 		}
    509 	}
    510 }
    511 
    512 /* journal_switch_revoke table select j_revoke for next transaction
    513  * we do not want to suspend any processing until all revokes are
    514  * written -bzzz
    515  */
    516 void journal_switch_revoke_table(journal_t *journal)
    517 {
    518 	int i;
    519 
    520 	if (journal->j_revoke == journal->j_revoke_table[0])
    521 		journal->j_revoke = journal->j_revoke_table[1];
    522 	else
    523 		journal->j_revoke = journal->j_revoke_table[0];
    524 
    525 	for (i = 0; i < journal->j_revoke->hash_size; i++)
    526 		INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
    527 }
    528 
    529 /*
    530  * Write revoke records to the journal for all entries in the current
    531  * revoke hash, deleting the entries as we go.
    532  */
    533 void journal_write_revoke_records(journal_t *journal,
    534 				       transaction_t *transaction,
    535 				       struct list_head *log_bufs,
    536 				       int write_op)
    537 {
    538 	struct buffer_head *descriptor;
    539 	struct jbd2_revoke_record_s *record;
    540 	struct jbd2_revoke_table_s *revoke;
    541 	struct list_head *hash_list;
    542 	int i, offset, count;
    543 
    544 	descriptor = NULL;
    545 	offset = 0;
    546 	count = 0;
    547 
    548 	/* select revoke table for committing transaction */
    549 	revoke = journal->j_revoke == journal->j_revoke_table[0] ?
    550 		journal->j_revoke_table[1] : journal->j_revoke_table[0];
    551 
    552 	for (i = 0; i < revoke->hash_size; i++) {
    553 		hash_list = &revoke->hash_table[i];
    554 
    555 		while (!list_empty(hash_list)) {
    556 			record = (struct jbd2_revoke_record_s *)
    557 				hash_list->next;
    558 			write_one_revoke_record(journal, transaction, log_bufs,
    559 						&descriptor, &offset,
    560 						record, write_op);
    561 			count++;
    562 			list_del(&record->hash);
    563 			kmem_cache_free(jbd2_revoke_record_cache, record);
    564 		}
    565 	}
    566 	if (descriptor)
    567 		flush_descriptor(journal, descriptor, offset, write_op);
    568 	jbd_debug(1, "Wrote %d revoke records\n", count);
    569 }
    570 
    571 /*
    572  * Write out one revoke record.  We need to create a new descriptor
    573  * block if the old one is full or if we have not already created one.
    574  */
    575 
    576 static void write_one_revoke_record(journal_t *journal,
    577 				    transaction_t *transaction,
    578 				    struct list_head *log_bufs,
    579 				    struct buffer_head **descriptorp,
    580 				    int *offsetp,
    581 				    struct jbd2_revoke_record_s *record,
    582 				    int write_op)
    583 {
    584 	int csum_size = 0;
    585 	struct buffer_head *descriptor;
    586 	int sz, offset;
    587 	journal_header_t *header;
    588 
    589 	/* If we are already aborting, this all becomes a noop.  We
    590            still need to go round the loop in
    591            journal_write_revoke_records in order to free all of the
    592            revoke records: only the IO to the journal is omitted. */
    593 	if (is_journal_aborted(journal))
    594 		return;
    595 
    596 	descriptor = *descriptorp;
    597 	offset = *offsetp;
    598 
    599 	/* Do we need to leave space at the end for a checksum? */
    600 	if (journal_has_csum_v2or3(journal))
    601 		csum_size = sizeof(struct journal_revoke_tail);
    602 
    603 	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
    604 		sz = 8;
    605 	else
    606 		sz = 4;
    607 
    608 	/* Make sure we have a descriptor with space left for the record */
    609 	if (descriptor) {
    610 		if (offset + sz > journal->j_blocksize - csum_size) {
    611 			flush_descriptor(journal, descriptor, offset, write_op);
    612 			descriptor = NULL;
    613 		}
    614 	}
    615 
    616 	if (!descriptor) {
    617 		descriptor = journal_get_descriptor_buffer(journal);
    618 		if (!descriptor)
    619 			return;
    620 		header = (journal_header_t *)descriptor->b_data;
    621 		header->h_magic     = ext2fs_cpu_to_be32(JFS_MAGIC_NUMBER);
    622 		header->h_blocktype = ext2fs_cpu_to_be32(JFS_REVOKE_BLOCK);
    623 		header->h_sequence  = ext2fs_cpu_to_be32(transaction->t_tid);
    624 
    625 		/* Record it so that we can wait for IO completion later */
    626 		BUFFER_TRACE(descriptor, "file in log_bufs");
    627 		jbd2_file_log_bh(log_bufs, descriptor);
    628 
    629 		offset = sizeof(journal_revoke_header_t);
    630 		*descriptorp = descriptor;
    631 	}
    632 
    633 	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT)) {
    634 		* ((__be64 *)(&descriptor->b_data[offset])) =
    635 			cpu_to_be64(record->blocknr);
    636 	else
    637 		* ((__be32 *)(&descriptor->b_data[offset])) =
    638 			cpu_to_be32(record->blocknr);
    639 	offset += sz;
    640 
    641 	*offsetp = offset;
    642 }
    643 
    644 static void jbd2_revoke_csum_set(journal_t *j, struct buffer_head *bh)
    645 {
    646 	struct journal_revoke_tail *tail;
    647 	__u32 csum;
    648 
    649 	if (!journal_has_csum_v2or3(j))
    650 		return;
    651 
    652 	tail = (struct journal_revoke_tail *)(bh->b_data + j->j_blocksize -
    653 			sizeof(struct journal_revoke_tail));
    654 	tail->r_checksum = 0;
    655 	csum = jbd2_chksum(j, j->j_csum_seed, bh->b_data, j->j_blocksize);
    656 	tail->r_checksum = ext2fs_cpu_to_be32(csum);
    657 }
    658 
    659 /*
    660  * Flush a revoke descriptor out to the journal.  If we are aborting,
    661  * this is a noop; otherwise we are generating a buffer which needs to
    662  * be waited for during commit, so it has to go onto the appropriate
    663  * journal buffer list.
    664  */
    665 
    666 static void flush_descriptor(journal_t *journal,
    667 			     struct buffer_head *descriptor,
    668 			     int offset, int write_op)
    669 {
    670 	journal_revoke_header_t *header;
    671 
    672 	if (is_journal_aborted(journal)) {
    673 		put_bh(descriptor);
    674 		return;
    675 	}
    676 
    677 	header = (journal_revoke_header_t *)descriptor->b_data;
    678 	header->r_count = ext2fs_cpu_to_be32(offset);
    679 	jbd2_revoke_csum_set(journal, descriptor);
    680 
    681 	set_buffer_jwrite(descriptor);
    682 	BUFFER_TRACE(descriptor, "write");
    683 	set_buffer_dirty(descriptor);
    684 	write_dirty_buffer(descriptor, write_op);
    685 }
    686 #endif
    687 
    688 /*
    689  * Revoke support for recovery.
    690  *
    691  * Recovery needs to be able to:
    692  *
    693  *  record all revoke records, including the tid of the latest instance
    694  *  of each revoke in the journal
    695  *
    696  *  check whether a given block in a given transaction should be replayed
    697  *  (ie. has not been revoked by a revoke record in that or a subsequent
    698  *  transaction)
    699  *
    700  *  empty the revoke table after recovery.
    701  */
    702 
    703 /*
    704  * First, setting revoke records.  We create a new revoke record for
    705  * every block ever revoked in the log as we scan it for recovery, and
    706  * we update the existing records if we find multiple revokes for a
    707  * single block.
    708  */
    709 
    710 int journal_set_revoke(journal_t *journal,
    711 		       unsigned long long blocknr,
    712 		       tid_t sequence)
    713 {
    714 	struct jbd2_revoke_record_s *record;
    715 
    716 	record = find_revoke_record(journal, blocknr);
    717 	if (record) {
    718 		/* If we have multiple occurrences, only record the
    719 		 * latest sequence number in the hashed record */
    720 		if (tid_gt(sequence, record->sequence))
    721 			record->sequence = sequence;
    722 		return 0;
    723 	}
    724 	return insert_revoke_hash(journal, blocknr, sequence);
    725 }
    726 
    727 /*
    728  * Test revoke records.  For a given block referenced in the log, has
    729  * that block been revoked?  A revoke record with a given transaction
    730  * sequence number revokes all blocks in that transaction and earlier
    731  * ones, but later transactions still need replayed.
    732  */
    733 
    734 int journal_test_revoke(journal_t *journal,
    735 			unsigned long long blocknr,
    736 			tid_t sequence)
    737 {
    738 	struct jbd2_revoke_record_s *record;
    739 
    740 	record = find_revoke_record(journal, blocknr);
    741 	if (!record)
    742 		return 0;
    743 	if (tid_gt(sequence, record->sequence))
    744 		return 0;
    745 	return 1;
    746 }
    747 
    748 /*
    749  * Finally, once recovery is over, we need to clear the revoke table so
    750  * that it can be reused by the running filesystem.
    751  */
    752 
    753 void journal_clear_revoke(journal_t *journal)
    754 {
    755 	int i;
    756 	struct list_head *hash_list;
    757 	struct jbd2_revoke_record_s *record;
    758 	struct jbd2_revoke_table_s *revoke;
    759 
    760 	revoke = journal->j_revoke;
    761 
    762 	for (i = 0; i < revoke->hash_size; i++) {
    763 		hash_list = &revoke->hash_table[i];
    764 		while (!list_empty(hash_list)) {
    765 			record = (struct jbd2_revoke_record_s*) hash_list->next;
    766 			list_del(&record->hash);
    767 			kmem_cache_free(jbd2_revoke_record_cache, record);
    768 		}
    769 	}
    770 }
    771