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|
/*
* linux/fs/jbd/revoke.c
*
* Written by Stephen C. Tweedie <sct@redhat.com>, 2000
*
* Copyright 2000 Red Hat corp --- All Rights Reserved
*
* This file is part of the Linux kernel and is made available under
* the terms of the GNU General Public License, version 2, or at your
* option, any later version, incorporated herein by reference.
*
* Journal revoke routines for the generic filesystem journaling code;
* part of the ext2fs journaling system.
*
* Revoke is the mechanism used to prevent old log records for deleted
* metadata from being replayed on top of newer data using the same
* blocks. The revoke mechanism is used in two separate places:
*
* + Commit: during commit we write the entire list of the current
* transaction's revoked blocks to the journal
*
* + Recovery: during recovery we record the transaction ID of all
* revoked blocks. If there are multiple revoke records in the log
* for a single block, only the last one counts, and if there is a log
* entry for a block beyond the last revoke, then that log entry still
* gets replayed.
*
* We can get interactions between revokes and new log data within a
* single transaction:
*
* Block is revoked and then journaled:
* The desired end result is the journaling of the new block, so we
* cancel the revoke before the transaction commits.
*
* Block is journaled and then revoked:
* The revoke must take precedence over the write of the block, so we
* need either to cancel the journal entry or to write the revoke
* later in the log than the log block. In this case, we choose the
* latter: journaling a block cancels any revoke record for that block
* in the current transaction, so any revoke for that block in the
* transaction must have happened after the block was journaled and so
* the revoke must take precedence.
*
* Block is revoked and then written as data:
* The data write is allowed to succeed, but the revoke is _not_
* cancelled. We still need to prevent old log records from
* overwriting the new data. We don't even need to clear the revoke
* bit here.
*
* Revoke information on buffers is a tri-state value:
*
* RevokeValid clear: no cached revoke status, need to look it up
* RevokeValid set, Revoked clear:
* buffer has not been revoked, and cancel_revoke
* need do nothing.
* RevokeValid set, Revoked set:
* buffer has been revoked.
*/
#ifndef __KERNEL__
#include "jfs_user.h"
#else
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/init.h>
#endif
#include <linux/log2.h>
static struct kmem_cache *revoke_record_cache;
static struct kmem_cache *revoke_table_cache;
/* Each revoke record represents one single revoked block. During
journal replay, this involves recording the transaction ID of the
last transaction to revoke this block. */
struct jbd_revoke_record_s
{
struct list_head hash;
tid_t sequence; /* Used for recovery only */
unsigned long blocknr;
};
/* The revoke table is just a simple hash table of revoke records. */
struct jbd_revoke_table_s
{
/* It is conceivable that we might want a larger hash table
* for recovery. Must be a power of two. */
int hash_size;
int hash_shift;
struct list_head *hash_table;
};
#ifdef __KERNEL__
static void write_one_revoke_record(journal_t *, transaction_t *,
struct journal_head **, int *,
struct jbd_revoke_record_s *);
static void flush_descriptor(journal_t *, struct journal_head *, int);
#endif
/* Utility functions to maintain the revoke table */
/* Borrowed from buffer.c: this is a tried and tested block hash function */
static inline int hash(journal_t *journal, unsigned long block)
{
struct jbd_revoke_table_s *table = journal->j_revoke;
int hash_shift = table->hash_shift;
return ((block << (hash_shift - 6)) ^
(block >> 13) ^
(block << (hash_shift - 12))) & (table->hash_size - 1);
}
static int insert_revoke_hash(journal_t *journal, unsigned long blocknr,
tid_t seq)
{
struct list_head *hash_list;
struct jbd_revoke_record_s *record;
repeat:
record = kmem_cache_alloc(revoke_record_cache, GFP_NOFS);
if (!record)
goto oom;
record->sequence = seq;
record->blocknr = blocknr;
hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
spin_lock(&journal->j_revoke_lock);
list_add(&record->hash, hash_list);
spin_unlock(&journal->j_revoke_lock);
return 0;
oom:
if (!journal_oom_retry)
return -ENOMEM;
jbd_debug(1, "ENOMEM in %s, retrying\n", __func__);
yield();
goto repeat;
}
/* Find a revoke record in the journal's hash table. */
static struct jbd_revoke_record_s *find_revoke_record(journal_t *journal,
unsigned long blocknr)
{
struct list_head *hash_list;
struct jbd_revoke_record_s *record;
hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
spin_lock(&journal->j_revoke_lock);
record = (struct jbd_revoke_record_s *) hash_list->next;
while (&(record->hash) != hash_list) {
if (record->blocknr == blocknr) {
spin_unlock(&journal->j_revoke_lock);
return record;
}
record = (struct jbd_revoke_record_s *) record->hash.next;
}
spin_unlock(&journal->j_revoke_lock);
return NULL;
}
int __init journal_init_revoke_caches(void)
{
revoke_record_cache = kmem_cache_create("revoke_record",
sizeof(struct jbd_revoke_record_s),
0,
SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY,
NULL);
if (!revoke_record_cache)
return -ENOMEM;
revoke_table_cache = kmem_cache_create("revoke_table",
sizeof(struct jbd_revoke_table_s),
0, SLAB_TEMPORARY, NULL);
if (!revoke_table_cache) {
kmem_cache_destroy(revoke_record_cache);
revoke_record_cache = NULL;
return -ENOMEM;
}
return 0;
}
void journal_destroy_revoke_caches(void)
{
kmem_cache_destroy(revoke_record_cache);
revoke_record_cache = NULL;
kmem_cache_destroy(revoke_table_cache);
revoke_table_cache = NULL;
}
/* Initialise the revoke table for a given journal to a given size. */
int journal_init_revoke(journal_t *journal, int hash_size)
{
int shift, tmp;
J_ASSERT (journal->j_revoke_table[0] == NULL);
shift = 0;
tmp = hash_size;
while((tmp >>= 1UL) != 0UL)
shift++;
journal->j_revoke_table[0] = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
if (!journal->j_revoke_table[0])
return -ENOMEM;
journal->j_revoke = journal->j_revoke_table[0];
/* Check that the hash_size is a power of two */
J_ASSERT(is_power_of_2(hash_size));
journal->j_revoke->hash_size = hash_size;
journal->j_revoke->hash_shift = shift;
journal->j_revoke->hash_table =
kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
if (!journal->j_revoke->hash_table) {
kmem_cache_free(revoke_table_cache, journal->j_revoke_table[0]);
journal->j_revoke = NULL;
return -ENOMEM;
}
for (tmp = 0; tmp < hash_size; tmp++)
INIT_LIST_HEAD(&journal->j_revoke->hash_table[tmp]);
journal->j_revoke_table[1] = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
if (!journal->j_revoke_table[1]) {
kfree(journal->j_revoke_table[0]->hash_table);
kmem_cache_free(revoke_table_cache, journal->j_revoke_table[0]);
return -ENOMEM;
}
|