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DEFINITIONS
This source file includes following definitions.
- hash
- insert_revoke_hash
- find_revoke_record
- journal_destroy_revoke_caches
- journal_init_revoke_caches
- journal_init_revoke_table
- journal_destroy_revoke_table
- journal_init_revoke
- journal_destroy_revoke
- journal_revoke
- journal_cancel_revoke
- journal_switch_revoke_table
- journal_write_revoke_records
- write_one_revoke_record
- flush_descriptor
- journal_set_revoke
- journal_test_revoke
- journal_clear_revoke
/*
* 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;
}
void journal_destroy_revoke_caches(void)
{
if (revoke_record_cache) {
kmem_cache_destroy(revoke_record_cache);
revoke_record_cache = NULL;
}
if (revoke_table_cache) {
kmem_cache_destroy(revoke_table_cache);
revoke_table_cache = NULL;
}
}
int __init journal_init_revoke_caches(void)
{
J_ASSERT(!revoke_record_cache);
J_ASSERT(!revoke_table_cache);
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)
goto record_cache_failure;
revoke_table_cache = kmem_cache_create("revoke_table",
sizeof(struct jbd_revoke_table_s),
0, SLAB_TEMPORARY, NULL);
if (!revoke_table_cache)
goto table_cache_failure;
return 0;
table_cache_failure:
journal_destroy_revoke_caches();
record_cache_failure:
return -ENOMEM;
}
static struct jbd_revoke_table_s *journal_init_revoke_table(int hash_size)
{
int shift = 0;
int tmp = hash_size;
struct jbd_revoke_table_s *table;
table = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
if (!table)
goto out;
while((tmp >>= 1UL) != 0UL)
shift++;
table->hash_size = hash_size;
table->hash_shift = shift;
table->hash_table =
kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
if (!table->hash_table) {
kmem_cache_free(revoke_table_cache, table);
table = NULL;
goto out;
}
for (tmp = 0; tmp < hash_size; tmp++)
INIT_LIST_HEAD(&table->hash_table[tmp]);
out:
return table;
}
static void journal_destroy_revoke_table(struct jbd_revoke_table_s *table)
{
int i;
struct list_head *hash_list;
for (i = 0; i < table->hash_size; i++) {
hash_list = &table->hash_table[i];
J_ASSERT(list_empty(hash_list));
}
kfree(table->hash_table);
kmem_cache_free(revoke_table_cache, table);
}
/* Initialise the revoke table for a given journal to a given size. */
int journal_init_revoke(journal_t *journal, int hash_size)
{
J_ASSERT(journal->j_revoke_table[0] == NULL);
J_ASSERT(is_power_of_2(hash_size));
journal->j_revoke_table[0] = journal_init_revoke_table(hash_size);
if (!journal->j_revoke_table[0])
goto fail0;
journal->j_revoke_table[1] = journal_init_revoke_table(hash_size);
if (!journal->j_revoke_table[1])
goto fail1;
journal->j_revoke = journal->j_revoke_table[1];
spin_lock_init(&journal->j_revoke_lock);
return 0;
fail1:
journal_destroy_revoke_table(journal->j_revoke_table[0]);
fail0:
return -ENOMEM;
}
/* Destroy a journal's revoke table. The table must already be empty! */
void journal_destroy_revoke(journal_t *journal)
{
journal->j_revoke = NULL;
if (journal->j_revoke_table[0])
journal_destroy_revoke_table(journal->j_revoke_table[0]);
if (journal->j_revoke_table[1])
journal_destroy_revoke_table(journal->j_revoke_table[1]);
}
#ifdef __KERNEL__
/*
* journal_revoke: revoke a given buffer_head from the journal. This
* prevents the block from being replayed during recovery if we take a
* crash after this current transaction commits. Any subsequent
* metadata writes of the buffer in this transaction cancel the
* revoke.
*
* Note that this call may block --- it is up to the caller to make
* sure that there are no further calls to journal_write_metadata
* before the revoke is complete. In ext3, this implies calling the
* revoke before clearing the block bitmap when we are deleting
* metadata.
*
* Revoke performs a journal_forget on any buffer_head passed in as a
* parameter, but does _not_ forget the buffer_head if the bh was only
* found implicitly.
*
* bh_in may not be a journalled buffer - it may have come off
* the hash tables without an attached journal_head.
*
* If bh_in is non-zero, journal_revoke() will decrement its b_count
* by one.
*/
int journal_revoke(handle_t *handle, unsigned long blocknr,
struct buffer_head *bh_in)
{
struct buffer_head *bh = NULL;
journal_t *journal;
struct block_device *bdev;
int err;
might_sleep();
if (bh_in)
BUFFER_TRACE(bh_in, "enter");
journal = handle->h_transaction->t_journal;
if (!journal_set_features(journal, 0, 0, JFS_FEATURE_INCOMPAT_REVOKE)){
J_ASSERT (!"Cannot set revoke feature!");
return -EINVAL;
}
bdev = journal->j_fs_dev;
bh = bh_in;
if (!bh) {
bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
if (bh)
BUFFER_TRACE(bh, "found on hash");
}
#ifdef JBD_EXPENSIVE_CHECKING
else {
struct buffer_head *bh2;
/* If there is a different buffer_head lying around in
* memory anywhere... */
bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
if (bh2) {
/* ... and it has RevokeValid status... */
if (bh2 != bh && buffer_revokevalid(bh2))
/* ...then it better be revoked too,
* since it's illegal to create a revoke
* record against a buffer_head which is
* not marked revoked --- that would
* risk missing a subsequent revoke
* cancel. */
J_ASSERT_BH(bh2, buffer_revoked(bh2));
put_bh(bh2);
}
}
#endif
/* We really ought not ever to revoke twice in a row without
first having the revoke cancelled: it's illegal to free a
block twice without allocating it in between! */
if (bh) {
if (!J_EXPECT_BH(bh, !buffer_revoked(bh),
"inconsistent data on disk")) {
if (!bh_in)
brelse(bh);
return -EIO;
}
set_buffer_revoked(bh);
set_buffer_revokevalid(bh);
if (bh_in) {
BUFFER_TRACE(bh_in, "call journal_forget");
journal_forget(handle, bh_in);
} else {
BUFFER_TRACE(bh, "call brelse");
__brelse(bh);
}
}
jbd_debug(2, "insert revoke for block %lu, bh_in=%p\n", blocknr, bh_in);
err = insert_revoke_hash(journal, blocknr,
handle->h_transaction->t_tid);
BUFFER_TRACE(bh_in, "exit");
return err;
}
/*
* Cancel an outstanding revoke. For use only internally by the
* journaling code (called from journal_get_write_access).
*
* We trust buffer_revoked() on the buffer if the buffer is already
* being journaled: if there is no revoke pending on the buffer, then we
* don't do anything here.
*
* This would break if it were possible for a buffer to be revoked and
* discarded, and then reallocated within the same transaction. In such
* a case we would have lost the revoked bit, but when we arrived here
* the second time we would still have a pending revoke to cancel. So,
* do not trust the Revoked bit on buffers unless RevokeValid is also
* set.
*
* The caller must have the journal locked.
*/
int journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
{
struct jbd_revoke_record_s *record;
journal_t *journal = handle->h_transaction->t_journal;
int need_cancel;
int did_revoke = 0; /* akpm: debug */
struct buffer_head *bh = jh2bh(jh);
jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
/* Is the existing Revoke bit valid? If so, we trust it, and
* only perform the full cancel if the revoke bit is set. If
* not, we can't trust the revoke bit, and we need to do the
* full search for a revoke record. */
if (test_set_buffer_revokevalid(bh)) {
need_cancel = test_clear_buffer_revoked(bh);
} else {
need_cancel = 1;
clear_buffer_revoked(bh);
}
if (need_cancel) {
record = find_revoke_record(journal, bh->b_blocknr);
if (record) {
jbd_debug(4, "cancelled existing revoke on "
"blocknr %llu\n", (unsigned long long)bh->b_blocknr);
spin_lock(&journal->j_revoke_lock);
list_del(&record->hash);
spin_unlock(&journal->j_revoke_lock);
kmem_cache_free(revoke_record_cache, record);
did_revoke = 1;
}
}
#ifdef JBD_EXPENSIVE_CHECKING
/* There better not be one left behind by now! */
record = find_revoke_record(journal, bh->b_blocknr);
J_ASSERT_JH(jh, record == NULL);
#endif
/* Finally, have we just cleared revoke on an unhashed
* buffer_head? If so, we'd better make sure we clear the
* revoked status on any hashed alias too, otherwise the revoke
* state machine will get very upset later on. */
if (need_cancel) {
struct buffer_head *bh2;
bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
if (bh2) {
if (bh2 != bh)
clear_buffer_revoked(bh2);
__brelse(bh2);
}
}
return did_revoke;
}
/* journal_switch_revoke table select j_revoke for next transaction
* we do not want to suspend any processing until all revokes are
* written -bzzz
*/
void journal_switch_revoke_table(journal_t *journal)
{
int i;
if (journal->j_revoke == journal->j_revoke_table[0])
journal->j_revoke = journal->j_revoke_table[1];
else
journal->j_revoke = journal->j_revoke_table[0];
for (i = 0; i < journal->j_revoke->hash_size; i++)
INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
}
/*
* Write revoke records to the journal for all entries in the current
* revoke hash, deleting the entries as we go.
*
* Called with the journal lock held.
*/
void journal_write_revoke_records(journal_t *journal,
transaction_t *transaction)
{
struct journal_head *descriptor;
struct jbd_revoke_record_s *record;
struct jbd_revoke_table_s *revoke;
struct list_head *hash_list;
int i, offset, count;
descriptor = NULL;
offset = 0;
count = 0;
/* select revoke table for committing transaction */
revoke = journal->j_revoke == journal->j_revoke_table[0] ?
journal->j_revoke_table[1] : journal->j_revoke_table[0];
for (i = 0; i < revoke->hash_size; i++) {
hash_list = &revoke->hash_table[i];
while (!list_empty(hash_list)) {
record = (struct jbd_revoke_record_s *)
hash_list->next;
write_one_revoke_record(journal, transaction,
&descriptor, &offset,
record);
count++;
list_del(&record->hash);
kmem_cache_free(revoke_record_cache, record);
}
}
if (descriptor)
flush_descriptor(journal, descriptor, offset);
jbd_debug(1, "Wrote %d revoke records\n", count);
}
/*
* Write out one revoke record. We need to create a new descriptor
* block if the old one is full or if we have not already created one.
*/
static void write_one_revoke_record(journal_t *journal,
transaction_t *transaction,
struct journal_head **descriptorp,
int *offsetp,
struct jbd_revoke_record_s *record)
{
struct journal_head *descriptor;
int offset;
journal_header_t *header;
/* If we are already aborting, this all becomes a noop. We
still need to go round the loop in
journal_write_revoke_records in order to free all of the
revoke records: only the IO to the journal is omitted. */
if (is_journal_aborted(journal))
return;
descriptor = *descriptorp;
offset = *offsetp;
/* Make sure we have a descriptor with space left for the record */
if (descriptor) {
if (offset == journal->j_blocksize) {
flush_descriptor(journal, descriptor, offset);
descriptor = NULL;
}
}
if (!descriptor) {
descriptor = journal_get_descriptor_buffer(journal);
if (!descriptor)
return;
header = (journal_header_t *) &jh2bh(descriptor)->b_data[0];
header->h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
header->h_blocktype = cpu_to_be32(JFS_REVOKE_BLOCK);
header->h_sequence = cpu_to_be32(transaction->t_tid);
/* Record it so that we can wait for IO completion later */
JBUFFER_TRACE(descriptor, "file as BJ_LogCtl");
journal_file_buffer(descriptor, transaction, BJ_LogCtl);
offset = sizeof(journal_revoke_header_t);
*descriptorp = descriptor;
}
* ((__be32 *)(&jh2bh(descriptor)->b_data[offset])) =
cpu_to_be32(record->blocknr);
offset += 4;
*offsetp = offset;
}
/*
* Flush a revoke descriptor out to the journal. If we are aborting,
* this is a noop; otherwise we are generating a buffer which needs to
* be waited for during commit, so it has to go onto the appropriate
* journal buffer list.
*/
static void flush_descriptor(journal_t *journal,
struct journal_head *descriptor,
int offset)
{
journal_revoke_header_t *header;
struct buffer_head *bh = jh2bh(descriptor);
if (is_journal_aborted(journal)) {
put_bh(bh);
return;
}
header = (journal_revoke_header_t *) jh2bh(descriptor)->b_data;
header->r_count = cpu_to_be32(offset);
set_buffer_jwrite(bh);
BUFFER_TRACE(bh, "write");
set_buffer_dirty(bh);
ll_rw_block(SWRITE, 1, &bh);
}
#endif
/*
* Revoke support for recovery.
*
* Recovery needs to be able to:
*
* record all revoke records, including the tid of the latest instance
* of each revoke in the journal
*
* check whether a given block in a given transaction should be replayed
* (ie. has not been revoked by a revoke record in that or a subsequent
* transaction)
*
* empty the revoke table after recovery.
*/
/*
* First, setting revoke records. We create a new revoke record for
* every block ever revoked in the log as we scan it for recovery, and
* we update the existing records if we find multiple revokes for a
* single block.
*/
int journal_set_revoke(journal_t *journal,
unsigned long blocknr,
tid_t sequence)
{
struct jbd_revoke_record_s *record;
record = find_revoke_record(journal, blocknr);
if (record) {
/* If we have multiple occurrences, only record the
* latest sequence number in the hashed record */
if (tid_gt(sequence, record->sequence))
record->sequence = sequence;
return 0;
}
return insert_revoke_hash(journal, blocknr, sequence);
}
/*
* Test revoke records. For a given block referenced in the log, has
* that block been revoked? A revoke record with a given transaction
* sequence number revokes all blocks in that transaction and earlier
* ones, but later transactions still need replayed.
*/
int journal_test_revoke(journal_t *journal,
unsigned long blocknr,
tid_t sequence)
{
struct jbd_revoke_record_s *record;
record = find_revoke_record(journal, blocknr);
if (!record)
return 0;
if (tid_gt(sequence, record->sequence))
return 0;
return 1;
}
/*
* Finally, once recovery is over, we need to clear the revoke table so
* that it can be reused by the running filesystem.
*/
void journal_clear_revoke(journal_t *journal)
{
int i;
struct list_head *hash_list;
struct jbd_revoke_record_s *record;
struct jbd_revoke_table_s *revoke;
revoke = journal->j_revoke;
for (i = 0; i < revoke->hash_size; i++) {
hash_list = &revoke->hash_table[i];
while (!list_empty(hash_list)) {
record = (struct jbd_revoke_record_s*) hash_list->next;
list_del(&record->hash);
kmem_cache_free(revoke_record_cache, record);
}
}
}