2
* linux/fs/jbd/revoke.c
4
* Written by Stephen C. Tweedie <sct@redhat.com>, 2000
6
* Copyright 2000 Red Hat corp --- All Rights Reserved
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.
12
* Journal revoke routines for the generic filesystem journaling code;
13
* part of the ext2fs journaling system.
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:
19
* + Commit: during commit we write the entire list of the current
20
* transaction's revoked blocks to the journal
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
28
* We can get interactions between revokes and new log data within a
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.
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.
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
50
* Revoke information on buffers is a tri-state value:
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* RevokeValid clear: no cached revoke status, need to look it up
53
* RevokeValid set, Revoked clear:
54
* buffer has not been revoked, and cancel_revoke
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* RevokeValid set, Revoked set:
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* buffer has been revoked.
60
* We keep two hash tables of revoke records. One hashtable belongs to the
61
* running transaction (is pointed to by journal->j_revoke), the other one
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* belongs to the committing transaction. Accesses to the second hash table
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* happen only from the kjournald and no other thread touches this table. Also
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* journal_switch_revoke_table() which switches which hashtable belongs to the
65
* running and which to the committing transaction is called only from
66
* kjournald. Therefore we need no locks when accessing the hashtable belonging
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* to the committing transaction.
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* All users operating on the hash table belonging to the running transaction
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* have a handle to the transaction. Therefore they are safe from kjournald
71
* switching hash tables under them. For operations on the lists of entries in
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* the hash table j_revoke_lock is used.
74
* Finally, also replay code uses the hash tables but at this moment no one else
75
* can touch them (filesystem isn't mounted yet) and hence no locking is
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#include <linux/time.h>
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#include <linux/jbd.h>
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#include <linux/errno.h>
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#include <linux/slab.h>
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#include <linux/list.h>
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#include <linux/init.h>
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#include <linux/bio.h>
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#include <linux/log2.h>
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static struct kmem_cache *revoke_record_cache;
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static struct kmem_cache *revoke_table_cache;
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/* Each revoke record represents one single revoked block. During
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journal replay, this involves recording the transaction ID of the
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last transaction to revoke this block. */
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struct jbd_revoke_record_s
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struct list_head hash;
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tid_t sequence; /* Used for recovery only */
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unsigned int blocknr;
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/* The revoke table is just a simple hash table of revoke records. */
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struct jbd_revoke_table_s
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/* It is conceivable that we might want a larger hash table
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* for recovery. Must be a power of two. */
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struct list_head *hash_table;
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static void write_one_revoke_record(journal_t *, transaction_t *,
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struct journal_head **, int *,
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struct jbd_revoke_record_s *, int);
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static void flush_descriptor(journal_t *, struct journal_head *, int, int);
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/* Utility functions to maintain the revoke table */
128
/* Borrowed from buffer.c: this is a tried and tested block hash function */
129
static inline int hash(journal_t *journal, unsigned int block)
131
struct jbd_revoke_table_s *table = journal->j_revoke;
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int hash_shift = table->hash_shift;
134
return ((block << (hash_shift - 6)) ^
136
(block << (hash_shift - 12))) & (table->hash_size - 1);
139
static int insert_revoke_hash(journal_t *journal, unsigned int blocknr,
142
struct list_head *hash_list;
143
struct jbd_revoke_record_s *record;
146
record = kmem_cache_alloc(revoke_record_cache, GFP_NOFS);
150
record->sequence = seq;
151
record->blocknr = blocknr;
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hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
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spin_lock(&journal->j_revoke_lock);
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list_add(&record->hash, hash_list);
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spin_unlock(&journal->j_revoke_lock);
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if (!journal_oom_retry)
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jbd_debug(1, "ENOMEM in %s, retrying\n", __func__);
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/* Find a revoke record in the journal's hash table. */
168
static struct jbd_revoke_record_s *find_revoke_record(journal_t *journal,
169
unsigned int blocknr)
171
struct list_head *hash_list;
172
struct jbd_revoke_record_s *record;
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hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
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spin_lock(&journal->j_revoke_lock);
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record = (struct jbd_revoke_record_s *) hash_list->next;
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while (&(record->hash) != hash_list) {
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if (record->blocknr == blocknr) {
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spin_unlock(&journal->j_revoke_lock);
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record = (struct jbd_revoke_record_s *) record->hash.next;
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spin_unlock(&journal->j_revoke_lock);
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void journal_destroy_revoke_caches(void)
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if (revoke_record_cache) {
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kmem_cache_destroy(revoke_record_cache);
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revoke_record_cache = NULL;
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if (revoke_table_cache) {
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kmem_cache_destroy(revoke_table_cache);
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revoke_table_cache = NULL;
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int __init journal_init_revoke_caches(void)
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J_ASSERT(!revoke_record_cache);
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J_ASSERT(!revoke_table_cache);
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revoke_record_cache = kmem_cache_create("revoke_record",
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sizeof(struct jbd_revoke_record_s),
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SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY,
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if (!revoke_record_cache)
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goto record_cache_failure;
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revoke_table_cache = kmem_cache_create("revoke_table",
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sizeof(struct jbd_revoke_table_s),
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0, SLAB_TEMPORARY, NULL);
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if (!revoke_table_cache)
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goto table_cache_failure;
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journal_destroy_revoke_caches();
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record_cache_failure:
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static struct jbd_revoke_table_s *journal_init_revoke_table(int hash_size)
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struct jbd_revoke_table_s *table;
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table = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
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while((tmp >>= 1UL) != 0UL)
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table->hash_size = hash_size;
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table->hash_shift = shift;
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kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
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if (!table->hash_table) {
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kmem_cache_free(revoke_table_cache, table);
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for (tmp = 0; tmp < hash_size; tmp++)
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INIT_LIST_HEAD(&table->hash_table[tmp]);
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static void journal_destroy_revoke_table(struct jbd_revoke_table_s *table)
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struct list_head *hash_list;
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for (i = 0; i < table->hash_size; i++) {
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hash_list = &table->hash_table[i];
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J_ASSERT(list_empty(hash_list));
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kfree(table->hash_table);
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kmem_cache_free(revoke_table_cache, table);
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/* Initialise the revoke table for a given journal to a given size. */
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int journal_init_revoke(journal_t *journal, int hash_size)
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J_ASSERT(journal->j_revoke_table[0] == NULL);
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J_ASSERT(is_power_of_2(hash_size));
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journal->j_revoke_table[0] = journal_init_revoke_table(hash_size);
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if (!journal->j_revoke_table[0])
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journal->j_revoke_table[1] = journal_init_revoke_table(hash_size);
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if (!journal->j_revoke_table[1])
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journal->j_revoke = journal->j_revoke_table[1];
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spin_lock_init(&journal->j_revoke_lock);
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journal_destroy_revoke_table(journal->j_revoke_table[0]);
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/* Destroy a journal's revoke table. The table must already be empty! */
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void journal_destroy_revoke(journal_t *journal)
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journal->j_revoke = NULL;
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if (journal->j_revoke_table[0])
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journal_destroy_revoke_table(journal->j_revoke_table[0]);
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if (journal->j_revoke_table[1])
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journal_destroy_revoke_table(journal->j_revoke_table[1]);
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* journal_revoke: revoke a given buffer_head from the journal. This
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* prevents the block from being replayed during recovery if we take a
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* crash after this current transaction commits. Any subsequent
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* metadata writes of the buffer in this transaction cancel the
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* Note that this call may block --- it is up to the caller to make
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* sure that there are no further calls to journal_write_metadata
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* before the revoke is complete. In ext3, this implies calling the
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* revoke before clearing the block bitmap when we are deleting
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* Revoke performs a journal_forget on any buffer_head passed in as a
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* parameter, but does _not_ forget the buffer_head if the bh was only
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* bh_in may not be a journalled buffer - it may have come off
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* the hash tables without an attached journal_head.
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* If bh_in is non-zero, journal_revoke() will decrement its b_count
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int journal_revoke(handle_t *handle, unsigned int blocknr,
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struct buffer_head *bh_in)
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struct buffer_head *bh = NULL;
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struct block_device *bdev;
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BUFFER_TRACE(bh_in, "enter");
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journal = handle->h_transaction->t_journal;
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if (!journal_set_features(journal, 0, 0, JFS_FEATURE_INCOMPAT_REVOKE)){
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J_ASSERT (!"Cannot set revoke feature!");
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bdev = journal->j_fs_dev;
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bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
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BUFFER_TRACE(bh, "found on hash");
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#ifdef JBD_EXPENSIVE_CHECKING
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struct buffer_head *bh2;
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/* If there is a different buffer_head lying around in
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* memory anywhere... */
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bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
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/* ... and it has RevokeValid status... */
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if (bh2 != bh && buffer_revokevalid(bh2))
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/* ...then it better be revoked too,
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* since it's illegal to create a revoke
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* record against a buffer_head which is
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* not marked revoked --- that would
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* risk missing a subsequent revoke
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J_ASSERT_BH(bh2, buffer_revoked(bh2));
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/* We really ought not ever to revoke twice in a row without
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first having the revoke cancelled: it's illegal to free a
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block twice without allocating it in between! */
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if (!J_EXPECT_BH(bh, !buffer_revoked(bh),
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"inconsistent data on disk")) {
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set_buffer_revoked(bh);
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set_buffer_revokevalid(bh);
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BUFFER_TRACE(bh_in, "call journal_forget");
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journal_forget(handle, bh_in);
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BUFFER_TRACE(bh, "call brelse");
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jbd_debug(2, "insert revoke for block %u, bh_in=%p\n", blocknr, bh_in);
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err = insert_revoke_hash(journal, blocknr,
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handle->h_transaction->t_tid);
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BUFFER_TRACE(bh_in, "exit");
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* Cancel an outstanding revoke. For use only internally by the
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* journaling code (called from journal_get_write_access).
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* We trust buffer_revoked() on the buffer if the buffer is already
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* being journaled: if there is no revoke pending on the buffer, then we
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* don't do anything here.
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
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* the second time we would still have a pending revoke to cancel. So,
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* do not trust the Revoked bit on buffers unless RevokeValid is also
426
int journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
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struct jbd_revoke_record_s *record;
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journal_t *journal = handle->h_transaction->t_journal;
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int did_revoke = 0; /* akpm: debug */
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struct buffer_head *bh = jh2bh(jh);
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jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
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/* 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
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* not, we can't trust the revoke bit, and we need to do the
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* full search for a revoke record. */
440
if (test_set_buffer_revokevalid(bh)) {
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need_cancel = test_clear_buffer_revoked(bh);
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clear_buffer_revoked(bh);
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record = find_revoke_record(journal, bh->b_blocknr);
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jbd_debug(4, "cancelled existing revoke on "
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"blocknr %llu\n", (unsigned long long)bh->b_blocknr);
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spin_lock(&journal->j_revoke_lock);
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list_del(&record->hash);
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spin_unlock(&journal->j_revoke_lock);
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kmem_cache_free(revoke_record_cache, record);
460
#ifdef JBD_EXPENSIVE_CHECKING
461
/* There better not be one left behind by now! */
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record = find_revoke_record(journal, bh->b_blocknr);
463
J_ASSERT_JH(jh, record == NULL);
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. */
471
struct buffer_head *bh2;
472
bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
475
clear_buffer_revoked(bh2);
482
/* journal_switch_revoke table select j_revoke for next transaction
483
* we do not want to suspend any processing until all revokes are
486
void journal_switch_revoke_table(journal_t *journal)
490
if (journal->j_revoke == journal->j_revoke_table[0])
491
journal->j_revoke = journal->j_revoke_table[1];
493
journal->j_revoke = journal->j_revoke_table[0];
495
for (i = 0; i < journal->j_revoke->hash_size; i++)
496
INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
500
* Write revoke records to the journal for all entries in the current
501
* revoke hash, deleting the entries as we go.
503
void journal_write_revoke_records(journal_t *journal,
504
transaction_t *transaction, int write_op)
506
struct journal_head *descriptor;
507
struct jbd_revoke_record_s *record;
508
struct jbd_revoke_table_s *revoke;
509
struct list_head *hash_list;
510
int i, offset, count;
516
/* select revoke table for committing transaction */
517
revoke = journal->j_revoke == journal->j_revoke_table[0] ?
518
journal->j_revoke_table[1] : journal->j_revoke_table[0];
520
for (i = 0; i < revoke->hash_size; i++) {
521
hash_list = &revoke->hash_table[i];
523
while (!list_empty(hash_list)) {
524
record = (struct jbd_revoke_record_s *)
526
write_one_revoke_record(journal, transaction,
527
&descriptor, &offset,
530
list_del(&record->hash);
531
kmem_cache_free(revoke_record_cache, record);
535
flush_descriptor(journal, descriptor, offset, write_op);
536
jbd_debug(1, "Wrote %d revoke records\n", count);
540
* Write out one revoke record. We need to create a new descriptor
541
* block if the old one is full or if we have not already created one.
544
static void write_one_revoke_record(journal_t *journal,
545
transaction_t *transaction,
546
struct journal_head **descriptorp,
548
struct jbd_revoke_record_s *record,
551
struct journal_head *descriptor;
553
journal_header_t *header;
555
/* If we are already aborting, this all becomes a noop. We
556
still need to go round the loop in
557
journal_write_revoke_records in order to free all of the
558
revoke records: only the IO to the journal is omitted. */
559
if (is_journal_aborted(journal))
562
descriptor = *descriptorp;
565
/* Make sure we have a descriptor with space left for the record */
567
if (offset == journal->j_blocksize) {
568
flush_descriptor(journal, descriptor, offset, write_op);
574
descriptor = journal_get_descriptor_buffer(journal);
577
header = (journal_header_t *) &jh2bh(descriptor)->b_data[0];
578
header->h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
579
header->h_blocktype = cpu_to_be32(JFS_REVOKE_BLOCK);
580
header->h_sequence = cpu_to_be32(transaction->t_tid);
582
/* Record it so that we can wait for IO completion later */
583
JBUFFER_TRACE(descriptor, "file as BJ_LogCtl");
584
journal_file_buffer(descriptor, transaction, BJ_LogCtl);
586
offset = sizeof(journal_revoke_header_t);
587
*descriptorp = descriptor;
590
* ((__be32 *)(&jh2bh(descriptor)->b_data[offset])) =
591
cpu_to_be32(record->blocknr);
597
* Flush a revoke descriptor out to the journal. If we are aborting,
598
* this is a noop; otherwise we are generating a buffer which needs to
599
* be waited for during commit, so it has to go onto the appropriate
600
* journal buffer list.
603
static void flush_descriptor(journal_t *journal,
604
struct journal_head *descriptor,
605
int offset, int write_op)
607
journal_revoke_header_t *header;
608
struct buffer_head *bh = jh2bh(descriptor);
610
if (is_journal_aborted(journal)) {
615
header = (journal_revoke_header_t *) jh2bh(descriptor)->b_data;
616
header->r_count = cpu_to_be32(offset);
617
set_buffer_jwrite(bh);
618
BUFFER_TRACE(bh, "write");
619
set_buffer_dirty(bh);
620
write_dirty_buffer(bh, write_op);
625
* Revoke support for recovery.
627
* Recovery needs to be able to:
629
* record all revoke records, including the tid of the latest instance
630
* of each revoke in the journal
632
* check whether a given block in a given transaction should be replayed
633
* (ie. has not been revoked by a revoke record in that or a subsequent
636
* empty the revoke table after recovery.
640
* First, setting revoke records. We create a new revoke record for
641
* every block ever revoked in the log as we scan it for recovery, and
642
* we update the existing records if we find multiple revokes for a
646
int journal_set_revoke(journal_t *journal,
647
unsigned int blocknr,
650
struct jbd_revoke_record_s *record;
652
record = find_revoke_record(journal, blocknr);
654
/* If we have multiple occurrences, only record the
655
* latest sequence number in the hashed record */
656
if (tid_gt(sequence, record->sequence))
657
record->sequence = sequence;
660
return insert_revoke_hash(journal, blocknr, sequence);
664
* Test revoke records. For a given block referenced in the log, has
665
* that block been revoked? A revoke record with a given transaction
666
* sequence number revokes all blocks in that transaction and earlier
667
* ones, but later transactions still need replayed.
670
int journal_test_revoke(journal_t *journal,
671
unsigned int blocknr,
674
struct jbd_revoke_record_s *record;
676
record = find_revoke_record(journal, blocknr);
679
if (tid_gt(sequence, record->sequence))
685
* Finally, once recovery is over, we need to clear the revoke table so
686
* that it can be reused by the running filesystem.
689
void journal_clear_revoke(journal_t *journal)
692
struct list_head *hash_list;
693
struct jbd_revoke_record_s *record;
694
struct jbd_revoke_table_s *revoke;
696
revoke = journal->j_revoke;
698
for (i = 0; i < revoke->hash_size; i++) {
699
hash_list = &revoke->hash_table[i];
700
while (!list_empty(hash_list)) {
701
record = (struct jbd_revoke_record_s*) hash_list->next;
702
list_del(&record->hash);
703
kmem_cache_free(revoke_record_cache, record);