*
* Atomicity of commits
* --------------------
- * In order to gaurantee atomicity during the commit operation, fast commit
+ * In order to guarantee atomicity during the commit operation, fast commit
* uses "EXT4_FC_TAG_TAIL" tag that marks a fast commit as complete. Tail
* tag contains CRC of the contents and TID of the transaction after which
* this fast commit should be applied. Recovery code replays fast commit
*
* Replay code should thus check for all the valid tails in the FC area.
*
+ * Fast Commit Replay Idempotence
+ * ------------------------------
+ *
+ * Fast commits tags are idempotent in nature provided the recovery code follows
+ * certain rules. The guiding principle that the commit path follows while
+ * committing is that it stores the result of a particular operation instead of
+ * storing the procedure.
+ *
+ * Let's consider this rename operation: 'mv /a /b'. Let's assume dirent '/a'
+ * was associated with inode 10. During fast commit, instead of storing this
+ * operation as a procedure "rename a to b", we store the resulting file system
+ * state as a "series" of outcomes:
+ *
+ * - Link dirent b to inode 10
+ * - Unlink dirent a
+ * - Inode <10> with valid refcount
+ *
+ * Now when recovery code runs, it needs "enforce" this state on the file
+ * system. This is what guarantees idempotence of fast commit replay.
+ *
+ * Let's take an example of a procedure that is not idempotent and see how fast
+ * commits make it idempotent. Consider following sequence of operations:
+ *
+ * rm A; mv B A; read A
+ * (x) (y) (z)
+ *
+ * (x), (y) and (z) are the points at which we can crash. If we store this
+ * sequence of operations as is then the replay is not idempotent. Let's say
+ * while in replay, we crash at (z). During the second replay, file A (which was
+ * actually created as a result of "mv B A" operation) would get deleted. Thus,
+ * file named A would be absent when we try to read A. So, this sequence of
+ * operations is not idempotent. However, as mentioned above, instead of storing
+ * the procedure fast commits store the outcome of each procedure. Thus the fast
+ * commit log for above procedure would be as follows:
+ *
+ * (Let's assume dirent A was linked to inode 10 and dirent B was linked to
+ * inode 11 before the replay)
+ *
+ * [Unlink A] [Link A to inode 11] [Unlink B] [Inode 11]
+ * (w) (x) (y) (z)
+ *
+ * If we crash at (z), we will have file A linked to inode 11. During the second
+ * replay, we will remove file A (inode 11). But we will create it back and make
+ * it point to inode 11. We won't find B, so we'll just skip that step. At this
+ * point, the refcount for inode 11 is not reliable, but that gets fixed by the
+ * replay of last inode 11 tag. Crashes at points (w), (x) and (y) get handled
+ * similarly. Thus, by converting a non-idempotent procedure into a series of
+ * idempotent outcomes, fast commits ensured idempotence during the replay.
+ *
* TODOs
* -----
+ *
+ * 0) Fast commit replay path hardening: Fast commit replay code should use
+ * journal handles to make sure all the updates it does during the replay
+ * path are atomic. With that if we crash during fast commit replay, after
+ * trying to do recovery again, we will find a file system where fast commit
+ * area is invalid (because new full commit would be found). In order to deal
+ * with that, fast commit replay code should ensure that the "FC_REPLAY"
+ * superblock state is persisted before starting the replay, so that after
+ * the crash, fast commit recovery code can look at that flag and perform
+ * fast commit recovery even if that area is invalidated by later full
+ * commits.
+ *
* 1) Make fast commit atomic updates more fine grained. Today, a fast commit
* eligible update must be protected within ext4_fc_start_update() and
* ext4_fc_stop_update(). These routines are called at much higher
INIT_LIST_HEAD(&ei->i_fc_list);
init_waitqueue_head(&ei->i_fc_wait);
atomic_set(&ei->i_fc_updates, 0);
- ei->i_fc_committed_subtid = 0;
+}
+
+/* This function must be called with sbi->s_fc_lock held. */
+static void ext4_fc_wait_committing_inode(struct inode *inode)
+__releases(&EXT4_SB(inode->i_sb)->s_fc_lock)
+{
+ wait_queue_head_t *wq;
+ struct ext4_inode_info *ei = EXT4_I(inode);
+
+#if (BITS_PER_LONG < 64)
+ DEFINE_WAIT_BIT(wait, &ei->i_state_flags,
+ EXT4_STATE_FC_COMMITTING);
+ wq = bit_waitqueue(&ei->i_state_flags,
+ EXT4_STATE_FC_COMMITTING);
+#else
+ DEFINE_WAIT_BIT(wait, &ei->i_flags,
+ EXT4_STATE_FC_COMMITTING);
+ wq = bit_waitqueue(&ei->i_flags,
+ EXT4_STATE_FC_COMMITTING);
+#endif
+ lockdep_assert_held(&EXT4_SB(inode->i_sb)->s_fc_lock);
+ prepare_to_wait(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE);
+ spin_unlock(&EXT4_SB(inode->i_sb)->s_fc_lock);
+ schedule();
+ finish_wait(wq, &wait.wq_entry);
}
/*
goto out;
if (ext4_test_inode_state(inode, EXT4_STATE_FC_COMMITTING)) {
- wait_queue_head_t *wq;
-#if (BITS_PER_LONG < 64)
- DEFINE_WAIT_BIT(wait, &ei->i_state_flags,
- EXT4_STATE_FC_COMMITTING);
- wq = bit_waitqueue(&ei->i_state_flags,
- EXT4_STATE_FC_COMMITTING);
-#else
- DEFINE_WAIT_BIT(wait, &ei->i_flags,
- EXT4_STATE_FC_COMMITTING);
- wq = bit_waitqueue(&ei->i_flags,
- EXT4_STATE_FC_COMMITTING);
-#endif
- prepare_to_wait(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE);
- spin_unlock(&EXT4_SB(inode->i_sb)->s_fc_lock);
- schedule();
- finish_wait(wq, &wait.wq_entry);
+ ext4_fc_wait_committing_inode(inode);
goto restart;
}
out:
}
if (ext4_test_inode_state(inode, EXT4_STATE_FC_COMMITTING)) {
- wait_queue_head_t *wq;
-#if (BITS_PER_LONG < 64)
- DEFINE_WAIT_BIT(wait, &ei->i_state_flags,
- EXT4_STATE_FC_COMMITTING);
- wq = bit_waitqueue(&ei->i_state_flags,
- EXT4_STATE_FC_COMMITTING);
-#else
- DEFINE_WAIT_BIT(wait, &ei->i_flags,
- EXT4_STATE_FC_COMMITTING);
- wq = bit_waitqueue(&ei->i_flags,
- EXT4_STATE_FC_COMMITTING);
-#endif
- prepare_to_wait(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE);
- spin_unlock(&EXT4_SB(inode->i_sb)->s_fc_lock);
- schedule();
- finish_wait(wq, &wait.wq_entry);
+ ext4_fc_wait_committing_inode(inode);
goto restart;
}
- if (!list_empty(&ei->i_fc_list))
- list_del_init(&ei->i_fc_list);
+ list_del_init(&ei->i_fc_list);
spin_unlock(&EXT4_SB(inode->i_sb)->s_fc_lock);
}
(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY))
return;
- sbi->s_mount_flags |= EXT4_MF_FC_INELIGIBLE;
+ ext4_set_mount_flag(sb, EXT4_MF_FC_INELIGIBLE);
WARN_ON(reason >= EXT4_FC_REASON_MAX);
sbi->s_fc_stats.fc_ineligible_reason_count[reason]++;
}
(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY))
return;
- EXT4_SB(sb)->s_mount_flags |= EXT4_MF_FC_INELIGIBLE;
+ ext4_set_mount_flag(sb, EXT4_MF_FC_INELIGIBLE);
atomic_dec(&EXT4_SB(sb)->s_fc_ineligible_updates);
}
static inline int ext4_fc_is_ineligible(struct super_block *sb)
{
- return (EXT4_SB(sb)->s_mount_flags & EXT4_MF_FC_INELIGIBLE) ||
- atomic_read(&EXT4_SB(sb)->s_fc_ineligible_updates);
+ return (ext4_test_mount_flag(sb, EXT4_MF_FC_INELIGIBLE) ||
+ atomic_read(&EXT4_SB(sb)->s_fc_ineligible_updates));
}
/*
* If enqueue is set, this function enqueues the inode in fast commit list.
*/
static int ext4_fc_track_template(
- struct inode *inode, int (*__fc_track_fn)(struct inode *, void *, bool),
+ handle_t *handle, struct inode *inode,
+ int (*__fc_track_fn)(struct inode *, void *, bool),
void *args, int enqueue)
{
- tid_t running_txn_tid;
bool update = false;
struct ext4_inode_info *ei = EXT4_I(inode);
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+ tid_t tid = 0;
int ret;
if (!test_opt2(inode->i_sb, JOURNAL_FAST_COMMIT) ||
if (ext4_fc_is_ineligible(inode->i_sb))
return -EINVAL;
- running_txn_tid = sbi->s_journal ?
- sbi->s_journal->j_commit_sequence + 1 : 0;
-
+ tid = handle->h_transaction->t_tid;
mutex_lock(&ei->i_fc_lock);
- if (running_txn_tid == ei->i_sync_tid) {
+ if (tid == ei->i_sync_tid) {
update = true;
} else {
ext4_fc_reset_inode(inode);
- ei->i_sync_tid = running_txn_tid;
+ ei->i_sync_tid = tid;
}
ret = __fc_track_fn(inode, args, update);
mutex_unlock(&ei->i_fc_lock);
spin_lock(&sbi->s_fc_lock);
if (list_empty(&EXT4_I(inode)->i_fc_list))
list_add_tail(&EXT4_I(inode)->i_fc_list,
- (sbi->s_mount_flags & EXT4_MF_FC_COMMITTING) ?
+ (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_COMMITTING)) ?
&sbi->s_fc_q[FC_Q_STAGING] :
&sbi->s_fc_q[FC_Q_MAIN]);
spin_unlock(&sbi->s_fc_lock);
mutex_unlock(&ei->i_fc_lock);
node = kmem_cache_alloc(ext4_fc_dentry_cachep, GFP_NOFS);
if (!node) {
- ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_MEM);
+ ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_NOMEM);
mutex_lock(&ei->i_fc_lock);
return -ENOMEM;
}
if (!node->fcd_name.name) {
kmem_cache_free(ext4_fc_dentry_cachep, node);
ext4_fc_mark_ineligible(inode->i_sb,
- EXT4_FC_REASON_MEM);
+ EXT4_FC_REASON_NOMEM);
mutex_lock(&ei->i_fc_lock);
return -ENOMEM;
}
node->fcd_name.len = dentry->d_name.len;
spin_lock(&sbi->s_fc_lock);
- if (sbi->s_mount_flags & EXT4_MF_FC_COMMITTING)
+ if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_COMMITTING))
list_add_tail(&node->fcd_list,
&sbi->s_fc_dentry_q[FC_Q_STAGING]);
else
return 0;
}
-void ext4_fc_track_unlink(struct inode *inode, struct dentry *dentry)
+void __ext4_fc_track_unlink(handle_t *handle,
+ struct inode *inode, struct dentry *dentry)
{
struct __track_dentry_update_args args;
int ret;
args.dentry = dentry;
args.op = EXT4_FC_TAG_UNLINK;
- ret = ext4_fc_track_template(inode, __track_dentry_update,
+ ret = ext4_fc_track_template(handle, inode, __track_dentry_update,
(void *)&args, 0);
trace_ext4_fc_track_unlink(inode, dentry, ret);
}
-void ext4_fc_track_link(struct inode *inode, struct dentry *dentry)
+void ext4_fc_track_unlink(handle_t *handle, struct dentry *dentry)
+{
+ __ext4_fc_track_unlink(handle, d_inode(dentry), dentry);
+}
+
+void __ext4_fc_track_link(handle_t *handle,
+ struct inode *inode, struct dentry *dentry)
{
struct __track_dentry_update_args args;
int ret;
args.dentry = dentry;
args.op = EXT4_FC_TAG_LINK;
- ret = ext4_fc_track_template(inode, __track_dentry_update,
+ ret = ext4_fc_track_template(handle, inode, __track_dentry_update,
(void *)&args, 0);
trace_ext4_fc_track_link(inode, dentry, ret);
}
-void ext4_fc_track_create(struct inode *inode, struct dentry *dentry)
+void ext4_fc_track_link(handle_t *handle, struct dentry *dentry)
+{
+ __ext4_fc_track_link(handle, d_inode(dentry), dentry);
+}
+
+void ext4_fc_track_create(handle_t *handle, struct dentry *dentry)
{
struct __track_dentry_update_args args;
+ struct inode *inode = d_inode(dentry);
int ret;
args.dentry = dentry;
args.op = EXT4_FC_TAG_CREAT;
- ret = ext4_fc_track_template(inode, __track_dentry_update,
+ ret = ext4_fc_track_template(handle, inode, __track_dentry_update,
(void *)&args, 0);
trace_ext4_fc_track_create(inode, dentry, ret);
}
return 0;
}
-void ext4_fc_track_inode(struct inode *inode)
+void ext4_fc_track_inode(handle_t *handle, struct inode *inode)
{
int ret;
if (S_ISDIR(inode->i_mode))
return;
- ret = ext4_fc_track_template(inode, __track_inode, NULL, 1);
+ if (ext4_should_journal_data(inode)) {
+ ext4_fc_mark_ineligible(inode->i_sb,
+ EXT4_FC_REASON_INODE_JOURNAL_DATA);
+ return;
+ }
+
+ ret = ext4_fc_track_template(handle, inode, __track_inode, NULL, 1);
trace_ext4_fc_track_inode(inode, ret);
}
return 0;
}
-void ext4_fc_track_range(struct inode *inode, ext4_lblk_t start,
+void ext4_fc_track_range(handle_t *handle, struct inode *inode, ext4_lblk_t start,
ext4_lblk_t end)
{
struct __track_range_args args;
args.start = start;
args.end = end;
- ret = ext4_fc_track_template(inode, __track_range, &args, 1);
+ ret = ext4_fc_track_template(handle, inode, __track_range, &args, 1);
trace_ext4_fc_track_range(inode, start, end, ret);
}
int write_flags = REQ_SYNC;
struct buffer_head *bh = EXT4_SB(sb)->s_fc_bh;
+ /* TODO: REQ_FUA | REQ_PREFLUSH is unnecessarily expensive. */
if (test_opt(sb, BARRIER))
write_flags |= REQ_FUA | REQ_PREFLUSH;
lock_buffer(bh);
- clear_buffer_dirty(bh);
+ set_buffer_dirty(bh);
set_buffer_uptodate(bh);
bh->b_end_io = ext4_end_buffer_io_sync;
submit_bh(REQ_OP_WRITE, write_flags, bh);
int ret = 0;
spin_lock(&sbi->s_fc_lock);
- sbi->s_mount_flags |= EXT4_MF_FC_COMMITTING;
+ ext4_set_mount_flag(sb, EXT4_MF_FC_COMMITTING);
list_for_each(pos, &sbi->s_fc_q[FC_Q_MAIN]) {
ei = list_entry(pos, struct ext4_inode_info, i_fc_list);
ext4_set_inode_state(&ei->vfs_inode, EXT4_STATE_FC_COMMITTING);
/* Commit all the directory entry updates */
static int ext4_fc_commit_dentry_updates(journal_t *journal, u32 *crc)
+__acquires(&sbi->s_fc_lock)
+__releases(&sbi->s_fc_lock)
{
struct super_block *sb = (struct super_block *)(journal->j_private);
struct ext4_sb_info *sbi = EXT4_SB(sb);
if (ret)
return ret;
+ /*
+ * If file system device is different from journal device, issue a cache
+ * flush before we start writing fast commit blocks.
+ */
+ if (journal->j_fs_dev != journal->j_dev)
+ blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS);
+
blk_start_plug(&plug);
if (sbi->s_fc_bytes == 0) {
/*
if (ret)
goto out;
spin_lock(&sbi->s_fc_lock);
- EXT4_I(inode)->i_fc_committed_subtid =
- atomic_read(&sbi->s_fc_subtid);
}
spin_unlock(&sbi->s_fc_lock);
"Fast commit ended with blks = %d, reason = %d, subtid - %d",
nblks, reason, subtid);
if (reason == EXT4_FC_REASON_FC_FAILED)
- return jbd2_fc_end_commit_fallback(journal, commit_tid);
+ return jbd2_fc_end_commit_fallback(journal);
if (reason == EXT4_FC_REASON_FC_START_FAILED ||
reason == EXT4_FC_REASON_INELIGIBLE)
return jbd2_complete_transaction(journal, commit_tid);
list_splice_init(&sbi->s_fc_q[FC_Q_STAGING],
&sbi->s_fc_q[FC_Q_STAGING]);
- sbi->s_mount_flags &= ~EXT4_MF_FC_COMMITTING;
- sbi->s_mount_flags &= ~EXT4_MF_FC_INELIGIBLE;
+ ext4_clear_mount_flag(sb, EXT4_MF_FC_COMMITTING);
+ ext4_clear_mount_flag(sb, EXT4_MF_FC_INELIGIBLE);
if (full)
sbi->s_fc_bytes = 0;
/* Ext4 Replay Path Routines */
-/* Get length of a particular tlv */
-static inline int ext4_fc_tag_len(struct ext4_fc_tl *tl)
-{
- return le16_to_cpu(tl->fc_len);
-}
-
-/* Get a pointer to "value" of a tlv */
-static inline u8 *ext4_fc_tag_val(struct ext4_fc_tl *tl)
-{
- return (u8 *)tl + sizeof(*tl);
-}
-
/* Helper struct for dentry replay routines */
struct dentry_info_args {
int parent_ino, dname_len, ino, inode_len;
return 0;
}
- ret = __ext4_unlink(old_parent, &entry, inode);
+ ret = __ext4_unlink(NULL, old_parent, &entry, inode);
/* -ENOENT ok coz it might not exist anymore. */
if (ret == -ENOENT)
ret = 0;
return 0;
}
-static inline const char *tag2str(u16 tag)
-{
- switch (tag) {
- case EXT4_FC_TAG_LINK:
- return "TAG_ADD_ENTRY";
- case EXT4_FC_TAG_UNLINK:
- return "TAG_DEL_ENTRY";
- case EXT4_FC_TAG_ADD_RANGE:
- return "TAG_ADD_RANGE";
- case EXT4_FC_TAG_CREAT:
- return "TAG_CREAT_DENTRY";
- case EXT4_FC_TAG_DEL_RANGE:
- return "TAG_DEL_RANGE";
- case EXT4_FC_TAG_INODE:
- return "TAG_INODE";
- case EXT4_FC_TAG_PAD:
- return "TAG_PAD";
- case EXT4_FC_TAG_TAIL:
- return "TAG_TAIL";
- case EXT4_FC_TAG_HEAD:
- return "TAG_HEAD";
- default:
- return "TAG_ERROR";
- }
-}
-
static void ext4_fc_set_bitmaps_and_counters(struct super_block *sb)
{
struct ext4_fc_replay_state *state;
void ext4_fc_init(struct super_block *sb, journal_t *journal)
{
- int num_fc_blocks;
-
/*
* We set replay callback even if fast commit disabled because we may
* could still have fast commit blocks that need to be replayed even if
if (!test_opt2(sb, JOURNAL_FAST_COMMIT))
return;
journal->j_fc_cleanup_callback = ext4_fc_cleanup;
- if (!buffer_uptodate(journal->j_sb_buffer)
- && ext4_read_bh_lock(journal->j_sb_buffer, REQ_META | REQ_PRIO,
- true)) {
- ext4_msg(sb, KERN_ERR, "I/O error on journal");
- return;
- }
- num_fc_blocks = be32_to_cpu(journal->j_superblock->s_num_fc_blks);
- if (jbd2_fc_init(journal, num_fc_blocks ? num_fc_blocks :
- EXT4_NUM_FC_BLKS)) {
- pr_warn("Error while enabling fast commits, turning off.");
- ext4_clear_feature_fast_commit(sb);
- }
}
-const char *fc_ineligible_reasons[] = {
+static const char *fc_ineligible_reasons[] = {
"Extended attributes changed",
"Cross rename",
"Journal flag changed",
"Resize",
"Dir renamed",
"Falloc range op",
+ "Data journalling",
"FC Commit Failed"
};
projects / linux.git / blobdiff