+++ /dev/null
-/*
- * 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.
- *
- * We cache revoke status of a buffer in the current transaction in b_states
- * bits. As the name says, revokevalid flag indicates that the cached revoke
- * status of a buffer is valid and we can rely on the cached status.
- *
- * 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.
- *
- * Locking rules:
- * We keep two hash tables of revoke records. One hashtable belongs to the
- * running transaction (is pointed to by journal->j_revoke), the other one
- * belongs to the committing transaction. Accesses to the second hash table
- * happen only from the kjournald and no other thread touches this table. Also
- * journal_switch_revoke_table() which switches which hashtable belongs to the
- * running and which to the committing transaction is called only from
- * kjournald. Therefore we need no locks when accessing the hashtable belonging
- * to the committing transaction.
- *
- * All users operating on the hash table belonging to the running transaction
- * have a handle to the transaction. Therefore they are safe from kjournald
- * switching hash tables under them. For operations on the lists of entries in
- * the hash table j_revoke_lock is used.
- *
- * Finally, also replay code uses the hash tables but at this moment no one else
- * can touch them (filesystem isn't mounted yet) and hence no locking is
- * needed.
- */
-
-#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>
-#include <linux/bio.h>
-#endif
-#include <linux/log2.h>
-#include <linux/hash.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 int 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 *, int);
-static void flush_descriptor(journal_t *, struct journal_head *, int, int);
-#endif
-
-/* Utility functions to maintain the revoke table */
-
-static inline int hash(journal_t *journal, unsigned int block)
-{
- struct jbd_revoke_table_s *table = journal->j_revoke;
-
- return hash_32(block, table->hash_shift);
-}
-
-static int insert_revoke_hash(journal_t *journal, unsigned int 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 int 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 i;
- struct jbd_revoke_table_s *table;
-
- table = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
- if (!table)
- goto out;
-
- table->hash_size = hash_size;
- table->hash_shift = ilog2(hash_size);
- 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 (i = 0; i < hash_size; i++)
- INIT_LIST_HEAD(&table->hash_table[i]);
-
-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 int 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 %u, 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.
- */
-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_clear_revoked_flags clears revoked flag of buffers in
- * revoke table to reflect there is no revoked buffer in the next
- * transaction which is going to be started.
- */
-void journal_clear_buffer_revoked_flags(journal_t *journal)
-{
- struct jbd_revoke_table_s *revoke = journal->j_revoke;
- int i = 0;
-
- for (i = 0; i < revoke->hash_size; i++) {
- struct list_head *hash_list;
- struct list_head *list_entry;
- hash_list = &revoke->hash_table[i];
-
- list_for_each(list_entry, hash_list) {
- struct jbd_revoke_record_s *record;
- struct buffer_head *bh;
- record = (struct jbd_revoke_record_s *)list_entry;
- bh = __find_get_block(journal->j_fs_dev,
- record->blocknr,
- journal->j_blocksize);
- if (bh) {
- clear_buffer_revoked(bh);
- __brelse(bh);
- }
- }
- }
-}
-
-/* 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.
- */
-void journal_write_revoke_records(journal_t *journal,
- transaction_t *transaction, int write_op)
-{
- 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, write_op);
- count++;
- list_del(&record->hash);
- kmem_cache_free(revoke_record_cache, record);
- }
- }
- if (descriptor)
- flush_descriptor(journal, descriptor, offset, write_op);
- 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,
- int write_op)
-{
- 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, write_op);
- 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, int write_op)
-{
- 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);
- write_dirty_buffer(bh, write_op);
-}
-#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 int 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 int 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);
- }
- }
-}
Code Review / kvmfornfv.git / blobdiff