With fast commits, if the entire commit is contained within a single
block and there isn't any data that needs a flush, we can avoid sending
expensive cache flush to disk. Single block metadata only fast commits
can be written using FUA to guarantee consistency.
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx>
---
fs/ext4/ext4.h | 12 ++++++++++++
fs/ext4/ext4_jbd2.h | 20 ++++++++++++--------
fs/ext4/fast_commit.c | 23 ++++++++++++++++++-----
3 files changed, 42 insertions(+), 13 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 196c513f82dd..3721daea2890 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1744,6 +1744,13 @@ struct ext4_sb_info {
*/
struct list_head s_fc_dentry_q[2]; /* directory entry updates */
unsigned int s_fc_bytes;
+
+ /*
+ * This flag indicates whether a full flush is needed on
+ * next fast commit.
+ */
+ int fc_flush_required;
+
/*
* Main fast commit lock. This lock protects accesses to the
* following fields:
@@ -2905,6 +2912,11 @@ void ext4_fc_del(struct inode *inode);
bool ext4_fc_replay_check_excluded(struct super_block *sb, ext4_fsblk_t block);
void ext4_fc_replay_cleanup(struct super_block *sb);
int ext4_fc_commit(journal_t *journal, tid_t commit_tid);
+static inline void ext4_fc_mark_needs_flush(struct super_block *sb)
+{
+ EXT4_SB(sb)->fc_flush_required = 1;
+}
+
int __init ext4_fc_init_dentry_cache(void);
void ext4_fc_destroy_dentry_cache(void);
int ext4_fc_record_regions(struct super_block *sb, int ino,
diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index 0c77697d5e90..e3a4f5c49b6e 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -420,19 +420,23 @@ static inline int ext4_journal_force_commit(journal_t *journal)
static inline int ext4_jbd2_inode_add_write(handle_t *handle,
struct inode *inode, loff_t start_byte, loff_t length)
{
- if (ext4_handle_valid(handle))
- return jbd2_journal_inode_ranged_write(handle,
- EXT4_I(inode)->jinode, start_byte, length);
- return 0;
+ if (!ext4_handle_valid(handle))
+ return 0;
+
+ ext4_fc_mark_needs_flush(inode->i_sb);
+ return jbd2_journal_inode_ranged_write(handle,
+ EXT4_I(inode)->jinode, start_byte, length);
}
static inline int ext4_jbd2_inode_add_wait(handle_t *handle,
struct inode *inode, loff_t start_byte, loff_t length)
{
- if (ext4_handle_valid(handle))
- return jbd2_journal_inode_ranged_wait(handle,
- EXT4_I(inode)->jinode, start_byte, length);
- return 0;
+ if (!ext4_handle_valid(handle))
+ return 0;
+
+ ext4_fc_mark_needs_flush(inode->i_sb);
+ return jbd2_journal_inode_ranged_wait(handle,
+ EXT4_I(inode)->jinode, start_byte, length);
}
static inline void ext4_update_inode_fsync_trans(handle_t *handle,
diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
index 0b7064f8dfa5..35c89bee452c 100644
--- a/fs/ext4/fast_commit.c
+++ b/fs/ext4/fast_commit.c
@@ -638,11 +638,24 @@ void ext4_fc_track_range(handle_t *handle, struct inode *inode, ext4_lblk_t star
static void ext4_fc_submit_bh(struct super_block *sb, bool is_tail)
{
blk_opf_t write_flags = REQ_SYNC;
- struct buffer_head *bh = EXT4_SB(sb)->s_fc_bh;
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct buffer_head *bh = sbi->s_fc_bh;
+ int old = 1, new = 0;
+
+ if (!is_tail) {
+ /*
+ * This commit has at least 1 non-tail block,
+ * thus FLUSH is required.
+ */
+ ext4_fc_mark_needs_flush(sb);
+ } else {
+ /* Use cmpxchg to ensure that no flush requrest is lost. */
+ if (cmpxchg(&sbi->fc_flush_required, old, new))
+ /* Old value was 1, so request a flush. */
+ write_flags |= REQ_PREFLUSH;
+ write_flags |= REQ_FUA;
+ }
- /* Add REQ_FUA | REQ_PREFLUSH only its tail */
- if (test_opt(sb, BARRIER) && is_tail)
- write_flags |= REQ_FUA | REQ_PREFLUSH;
lock_buffer(bh);
set_buffer_dirty(bh);
set_buffer_uptodate(bh);
@@ -1090,7 +1103,7 @@ static int ext4_fc_perform_commit(journal_t *journal)
* 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)
+ if (sbi->fc_flush_required && journal->j_fs_dev != journal->j_dev)
blkdev_issue_flush(journal->j_fs_dev);
blk_start_plug(&plug);
--
2.45.0.rc1.225.g2a3ae87e7f-goog
