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/*
* linux/fs/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
* former: the commit code must skip any block that has the Revoke bit
* set.
*
* 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, Revoke clear:
* buffer has not been revoked, and cancel_revoke
* need do nothing.
* RevokeValid set, Revoke set:
* buffer has been revoked.
*/
#ifndef __KERNEL__
#include "jfs_user.h"
#else
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/jfs.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/locks.h>
#include <linux/buffer.h>
#include <linux/list.h>
#endif
static kmem_cache_t *revoke_record_cache;
static kmem_cache_t *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 jfs_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 jfs_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 buffer_head **, int *,
struct jfs_revoke_record_s *);
static void flush_descriptor(journal_t *, struct buffer_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 jfs_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 jfs_revoke_record_s *record;
record = kmem_cache_alloc(revoke_record_cache, GFP_KERNEL);
if (!record)
return -ENOMEM;
record->sequence = seq;
record->blocknr = blocknr;
hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
list_add(&record->hash, hash_list);
return 0;
}
/* Find a revoke record in the journal's hash table. */
static struct jfs_revoke_record_s *find_revoke_record(journal_t *journal,
unsigned long blocknr)
{
struct list_head *hash_list;
struct jfs_revoke_record_s *record;
hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
record = (struct jfs_revoke_record_s *) hash_list->next;
while (&(record->hash) != hash_list) {
if (record->blocknr == blocknr)
return record;
record = (struct jfs_revoke_record_s *) record->hash.next;
}
return 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 == NULL);
if (!revoke_record_cache)
revoke_record_cache =
kmem_cache_create ("revoke_record",
sizeof(struct jfs_revoke_record_s),
0, SLAB_HWCACHE_ALIGN, NULL, NULL);
if (!revoke_table_cache)
revoke_table_cache =
kmem_cache_create ("revoke_table",
sizeof(struct jfs_revoke_table_s),
0, 0, NULL, NULL);
if (!revoke_record_cache || !revoke_table_cache)
return -ENOMEM;
journal->j_revoke = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
if (!journal->j_revoke)
return -ENOMEM;
/* Check that the hash_size is a power of two */
J_ASSERT ((hash_size & (hash_size-1)) == 0);
journal->j_revoke->hash_size = hash_size;
shift = 0;
tmp = hash_size;
while((tmp >>= 1UL) != 0UL)
shift++;
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);
journal->j_revoke = NULL;
return -ENOMEM;
}
for (tmp = 0; tmp < hash_size; tmp++)
INIT_LIST_HEAD(&journal->j_revoke->hash_table[tmp]);
return 0;
}
/* Destoy a journal's revoke table. The table must already be empty! */
void journal_destroy_revoke(journal_t *journal)
{
struct jfs_revoke_table_s *table;
struct list_head *hash_list;
int i;
table = journal->j_revoke;
if (!table)
return;
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);
journal->j_revoke = NULL;
}
#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.
*
* Revoke must observe the same synchronisation rules as bforget: it
* must not discard the buffer once it has blocked.
*/
int journal_revoke(handle_t *handle, unsigned long blocknr,
struct buffer_head *bh_in)
{
struct buffer_head *bh;
journal_t *journal;
kdev_t dev;
int err;
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;
}
dev = journal->j_dev;
bh = bh_in;
if (!bh)
bh = get_hash_table(dev, blocknr, journal->j_blocksize);
/* 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) {
J_ASSERT (!test_and_set_bit(BH_Revoked, &bh->b_state));
set_bit(BH_RevokeValid, &bh->b_state);
if (bh_in)
journal_forget(handle, bh_in);
else
brelse(bh);
}
lock_journal(journal);
err = insert_revoke_hash(journal, blocknr,
handle->h_transaction->t_tid);
unlock_journal(journal);
return err;
}
/*
* Cancel an outstanding revoke. For use only internally by the
* journaling code (called from journal_get_write_access).
*
* We trust the BH_Revoked bit 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.
* */
void journal_cancel_revoke(handle_t *handle, struct buffer_head *bh)
{
struct jfs_revoke_record_s *record;
journal_t *journal = handle->h_transaction->t_journal;
int need_cancel;
J_ASSERT (journal->j_locked);
/* 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_and_set_bit(BH_RevokeValid, &bh->b_state))
need_cancel = (test_and_clear_bit(BH_Revoked, &bh->b_state));
else {
need_cancel = 1;
clear_bit(BH_Revoked, &bh->b_state);
}
if (need_cancel) {
record = find_revoke_record(journal, bh->b_blocknr);
if (record) {
list_del(&record->hash);
kmem_cache_free(revoke_record_cache, record);
}
}
}
/*
* 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 buffer_head *descriptor;
struct jfs_revoke_record_s *record;
struct jfs_revoke_table_s *revoke;
struct list_head *hash_list;
int i, offset, count;
descriptor = NULL;
offset = 0;
count = 0;
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 jfs_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);
jfs_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 buffer_head **descriptorp,
int *offsetp,
struct jfs_revoke_record_s *record)
{
struct buffer_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_abort(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);
header = (journal_header_t *) &descriptor->b_data[0];
header->h_magic = htonl(JFS_MAGIC_NUMBER);
header->h_blocktype = htonl(JFS_REVOKE_BLOCK);
header->h_sequence = htonl(transaction->t_tid);
/* Record it so that we can wait for IO completion later */
journal_file_buffer(descriptor, transaction, BJ_LogCtl);
offset = sizeof(journal_revoke_header_t);
*descriptorp = descriptor;
}
* ((unsigned int *)(&descriptor->b_data[offset])) =
htonl(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 buffer_head *descriptor,
int offset)
{
journal_revoke_header_t *header;
if (is_journal_abort(journal)) {
brelse(descriptor);
return;
}
header = (journal_revoke_header_t *) descriptor->b_data;
header->r_count = htonl(offset);
set_bit(BH_JWrite, &descriptor->b_state);
ll_rw_block (WRITE, 1, &descriptor);
}
#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 jfs_revoke_record_s *record;
record = find_revoke_record(journal, blocknr);
if (record) {
/* If we have multiple occurences, only record the
* latest sequence number in the hashed record */
if (tid_ge(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 jfs_revoke_record_s *record;
record = find_revoke_record(journal, blocknr);
if (!record)
return 0;
if (tid_ge(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 jfs_revoke_record_s *record;
struct jfs_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 jfs_revoke_record_s*) hash_list->next;
list_del(&record->hash);
kmem_cache_free(revoke_record_cache, record);
}
}
}