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// SPDX-License-Identifier: GPL-2.0+
/*
* linux/fs/jbd2/revoke.c
*
* Written by Stephen C. Tweedie <sct@redhat.com>, 2000
*
* Copyright 2000 Red Hat corp --- All Rights Reserved
*
* 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* buffer has not been revoked, and cancel_revoke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* buffer has been revoked.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/jbd2.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/bio.h>
#include <linux/log2.h>
#include <linux/hash.h>
#endif
static struct kmem_cache *jbd2_revoke_record_cache;
static struct kmem_cache *jbd2_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 jbd2_revoke_record_s
{
struct list_head hash;
tid_t sequence; /* Used for recovery only */
unsigned long long blocknr;
};
/* The revoke table is just a simple hash table of revoke records. */
struct jbd2_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(transaction_t *,
struct list_head *,
struct buffer_head **, int *,
struct jbd2_revoke_record_s *);
static void flush_descriptor(journal_t *, struct buffer_head *, int);
#endif
/* Utility functions to maintain the revoke table */
static inline int hash(journal_t *journal, unsigned long long block)
{
return hash_64(block, journal->j_revoke->hash_shift);
}
static int insert_revoke_hash(journal_t *journal, unsigned long long blocknr,
tid_t seq)
{
struct list_head *hash_list;
struct jbd2_revoke_record_s *record;
gfp_t gfp_mask = GFP_NOFS;
if (journal_oom_retry)
gfp_mask |= __GFP_NOFAIL;
record = kmem_cache_alloc(jbd2_revoke_record_cache, gfp_mask);
if (!record)
return -ENOMEM;
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;
}
/* Find a revoke record in the journal's hash table. */
static struct jbd2_revoke_record_s *find_revoke_record(journal_t *journal,
unsigned long long blocknr)
{
struct list_head *hash_list;
struct jbd2_revoke_record_s *record;
hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
spin_lock(&journal->j_revoke_lock);
record = (struct jbd2_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 jbd2_revoke_record_s *) record->hash.next;
}
spin_unlock(&journal->j_revoke_lock);
return NULL;
}
void jbd2_journal_destroy_revoke_record_cache(void)
{
kmem_cache_destroy(jbd2_revoke_record_cache);
jbd2_revoke_record_cache = NULL;
}
void jbd2_journal_destroy_revoke_table_cache(void)
{
kmem_cache_destroy(jbd2_revoke_table_cache);
jbd2_revoke_table_cache = NULL;
}
int __init jbd2_journal_init_revoke_record_cache(void)
{
J_ASSERT(!jbd2_revoke_record_cache);
jbd2_revoke_record_cache = KMEM_CACHE(jbd2_revoke_record_s,
SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY);
if (!jbd2_revoke_record_cache) {
pr_emerg("JBD2: failed to create revoke_record cache\n");
return -ENOMEM;
}
return 0;
}
int __init jbd2_journal_init_revoke_table_cache(void)
{
J_ASSERT(!jbd2_revoke_table_cache);
jbd2_revoke_table_cache = KMEM_CACHE(jbd2_revoke_table_s,
SLAB_TEMPORARY);
if (!jbd2_revoke_table_cache) {
pr_emerg("JBD2: failed to create revoke_table cache\n");
return -ENOMEM;
}
return 0;
}
static struct jbd2_revoke_table_s *jbd2_journal_init_revoke_table(int hash_size)
{
int shift = 0;
int tmp = hash_size;
struct jbd2_revoke_table_s *table;
table = kmem_cache_alloc(jbd2_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_array(hash_size, sizeof(struct list_head), GFP_KERNEL);
if (!table->hash_table) {
kmem_cache_free(jbd2_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 jbd2_journal_destroy_revoke_table(struct jbd2_revoke_table_s *table)
{
int i;
struct list_head *hash_list;
for (i = 0; i < table->hash_size;
|