/* * linux/fs/jbd2/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* * RevokeValid clear: no cached revoke status, need to look it up * RevokeValid set, Revoked clear: * buffer has not been revoked, and cancel_revoke * need do nothing. * RevokeValid set, Revoked set: * buffer has been revoked. * * 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 noone 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> #endif #include <linux/log2.h> 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(journal_t *, transaction_t *, struct journal_head **, int *, struct jbd2_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 long long block) { struct jbd2_revoke_table_s *table = journal->j_revoke; int hash_shift = table->hash_shift; int hash = (int)block ^ (int)((block >> 31) >> 1); return ((hash << (hash_shift - 6)) ^ (hash >> 13) ^ (hash << (hash_shift - 12))) & (table->hash_size - 1); } 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; repeat: record = kmem_cache_alloc(jbd2_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 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_caches(void) { if (jbd2_revoke_record_cache) { kmem_cache_destroy(jbd2_revoke_record_cache); jbd2_revoke_record_cache = NULL; } if (jbd2_revoke_table_cache) { kmem_cache_destroy(jbd2_revoke_table_cache); jbd2_revoke_table_cache = NULL; } } int __init jbd2_journal_init_revoke_caches(void) { J_ASSERT(!jbd2_revoke_record_cache); J_ASSERT(!jbd2_revoke_table_cache); jbd2_revoke_record_cache = kmem_cache_create("jbd2_revoke_record", sizeof(struct jbd2_revoke_record_s), 0, SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY, NULL); if (!jbd2_revoke_record_cache) goto record_cache_failure; jbd2_revoke_table_cache = kmem_cache_create("jbd2_revoke_table", sizeof(struct jbd2_revoke_table_s), 0, SLAB_TEMPORARY, NULL); if (!jbd2_revoke_table_cache) goto table_cache_failure; return 0; table_cache_failure: jbd2_journal_destroy_revoke_caches(); record_cache_failure: return -ENOMEM; } 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(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; i++) { hash_list = &table->hash_table[i]; J_ASSERT(list_empty(hash_list)); } kfree(table->hash_table); kmem_cache_free(jbd2_revoke_table_cache, table); } /* Initialise the revoke table for a given journal to a given size. */ int jbd2_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] = jbd2_journal_init_revoke_table(hash_size); if (!journal->j_revoke_table[0]) goto fail0; journal->j_revoke_table[1] = jbd2_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: jbd2_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 jbd2_journal_destroy_revoke(journal_t *journal) { journal->j_revoke = NULL; if (journal->j_revoke_table[0]) jbd2_journal_destroy_revoke_table(journal->j_revoke_table[0]); if (journal->j_revoke_table[1]) jbd2_journal_destroy_revoke_table(journal->j_revoke_table[1]); } #ifdef __KERNEL__ /* * jbd2_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 jbd2_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, jbd2_journal_revoke() will decrement its b_count * by one. */ int jbd2_journal_revoke(handle_t *handle, unsigned long 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 (!jbd2_journal_set_features(journal, 0, 0, JBD2_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 JBD2_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 jbd2_journal_forget"); jbd2_journal_forget(handle, bh_in); } else { BUFFER_TRACE(bh, "call brelse"); __brelse(bh); } } jbd_debug(2, "insert revoke for block %llu, 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 jbd2_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 jbd2_journal_cancel_revoke(handle_t *handle, struct journal_head *jh) { struct jbd2_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(jbd2_revoke_record_cache, record); did_revoke = 1; } } #ifdef JBD2_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 jbd2_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 jbd2_journal_write_revoke_records(journal_t *journal, transaction_t *transaction, int write_op) { struct journal_head *descriptor; struct jbd2_revoke_record_s *record; struct jbd2_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 jbd2_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(jbd2_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 jbd2_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 jbd2_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 = jbd2_journal_get_descriptor_buffer(journal); if (!descriptor) return; header = (journal_header_t *) &jh2bh(descriptor)->b_data[0]; header->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER); header->h_blocktype = cpu_to_be32(JBD2_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"); jbd2_journal_file_buffer(descriptor, transaction, BJ_LogCtl); offset = sizeof(jbd2_journal_revoke_header_t); *descriptorp = descriptor; } if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT)) { * ((__be64 *)(&jh2bh(descriptor)->b_data[offset])) = cpu_to_be64(record->blocknr); offset += 8; } else { * ((__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) { jbd2_journal_revoke_header_t *header; struct buffer_head *bh = jh2bh(descriptor); if (is_journal_aborted(journal)) { put_bh(bh); return; } header = (jbd2_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((write_op == WRITE) ? SWRITE : SWRITE_SYNC_PLUG, 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 jbd2_journal_set_revoke(journal_t *journal, unsigned long long blocknr, tid_t sequence) { struct jbd2_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 jbd2_journal_test_revoke(journal_t *journal, unsigned long long blocknr, tid_t sequence) { struct jbd2_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 jbd2_journal_clear_revoke(journal_t *journal) { int i; struct list_head *hash_list; struct jbd2_revoke_record_s *record; struct jbd2_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 jbd2_revoke_record_s*) hash_list->next; list_del(&record->hash); kmem_cache_free(jbd2_revoke_record_cache, record); } } }