diff options
Diffstat (limited to 'fs/jbd/revoke.c')
| -rw-r--r-- | fs/jbd/revoke.c | 740 |
1 files changed, 740 insertions, 0 deletions
diff --git a/fs/jbd/revoke.c b/fs/jbd/revoke.c new file mode 100644 index 00000000..25c713e7 --- /dev/null +++ b/fs/jbd/revoke.c @@ -0,0 +1,740 @@ +/* + * 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> + +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 */ + +/* Borrowed from buffer.c: this is a tried and tested block hash function */ +static inline int hash(journal_t *journal, unsigned int 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 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 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 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); + } + } +} |