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ext4: simplify updating of fast commit stats
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[ Upstream commit 0915e46 ]

Move fast commit stats updating logic to a separate function from
ext4_fc_commit(). This significantly improves readability of
ext4_fc_commit().

Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20211223202140.2061101-4-harshads@google.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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harshadjs authored and gregkh committed Mar 8, 2022
1 parent c50a819 commit 5a30f59
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Showing 3 changed files with 68 additions and 59 deletions.
1 change: 0 additions & 1 deletion fs/ext4/ext4.h
Expand Up @@ -1747,7 +1747,6 @@ struct ext4_sb_info {
spinlock_t s_fc_lock;
struct buffer_head *s_fc_bh;
struct ext4_fc_stats s_fc_stats;
u64 s_fc_avg_commit_time;
#ifdef CONFIG_EXT4_DEBUG
int s_fc_debug_max_replay;
#endif
Expand Down
99 changes: 54 additions & 45 deletions fs/ext4/fast_commit.c
Expand Up @@ -1075,6 +1075,32 @@ static int ext4_fc_perform_commit(journal_t *journal)
return ret;
}

static void ext4_fc_update_stats(struct super_block *sb, int status,
u64 commit_time, int nblks)
{
struct ext4_fc_stats *stats = &EXT4_SB(sb)->s_fc_stats;

jbd_debug(1, "Fast commit ended with status = %d", status);
if (status == EXT4_FC_STATUS_OK) {
stats->fc_num_commits++;
stats->fc_numblks += nblks;
if (likely(stats->s_fc_avg_commit_time))
stats->s_fc_avg_commit_time =
(commit_time +
stats->s_fc_avg_commit_time * 3) / 4;
else
stats->s_fc_avg_commit_time = commit_time;
} else if (status == EXT4_FC_STATUS_FAILED ||
status == EXT4_FC_STATUS_INELIGIBLE) {
if (status == EXT4_FC_STATUS_FAILED)
stats->fc_failed_commits++;
stats->fc_ineligible_commits++;
} else {
stats->fc_skipped_commits++;
}
trace_ext4_fc_commit_stop(sb, nblks, status);
}

/*
* The main commit entry point. Performs a fast commit for transaction
* commit_tid if needed. If it's not possible to perform a fast commit
Expand All @@ -1087,7 +1113,7 @@ int ext4_fc_commit(journal_t *journal, tid_t commit_tid)
struct ext4_sb_info *sbi = EXT4_SB(sb);
int nblks = 0, ret, bsize = journal->j_blocksize;
int subtid = atomic_read(&sbi->s_fc_subtid);
int reason = EXT4_FC_REASON_OK, fc_bufs_before = 0;
int status = EXT4_FC_STATUS_OK, fc_bufs_before = 0;
ktime_t start_time, commit_time;

trace_ext4_fc_commit_start(sb);
Expand All @@ -1104,69 +1130,52 @@ int ext4_fc_commit(journal_t *journal, tid_t commit_tid)
if (atomic_read(&sbi->s_fc_subtid) <= subtid &&
commit_tid > journal->j_commit_sequence)
goto restart_fc;
reason = EXT4_FC_REASON_ALREADY_COMMITTED;
goto out;
ext4_fc_update_stats(sb, EXT4_FC_STATUS_SKIPPED, 0, 0);
return 0;
} else if (ret) {
sbi->s_fc_stats.fc_ineligible_reason_count[EXT4_FC_COMMIT_FAILED]++;
reason = EXT4_FC_REASON_FC_START_FAILED;
goto out;
/*
* Commit couldn't start. Just update stats and perform a
* full commit.
*/
ext4_fc_update_stats(sb, EXT4_FC_STATUS_FAILED, 0, 0);
return jbd2_complete_transaction(journal, commit_tid);
}

/*
* After establishing journal barrier via jbd2_fc_begin_commit(), check
* if we are fast commit ineligible.
*/
if (ext4_test_mount_flag(sb, EXT4_MF_FC_INELIGIBLE)) {
reason = EXT4_FC_REASON_INELIGIBLE;
goto out;
status = EXT4_FC_STATUS_INELIGIBLE;
goto fallback;
}

fc_bufs_before = (sbi->s_fc_bytes + bsize - 1) / bsize;
ret = ext4_fc_perform_commit(journal);
if (ret < 0) {
sbi->s_fc_stats.fc_ineligible_reason_count[EXT4_FC_COMMIT_FAILED]++;
reason = EXT4_FC_REASON_FC_FAILED;
goto out;
status = EXT4_FC_STATUS_FAILED;
goto fallback;
}
nblks = (sbi->s_fc_bytes + bsize - 1) / bsize - fc_bufs_before;
ret = jbd2_fc_wait_bufs(journal, nblks);
if (ret < 0) {
sbi->s_fc_stats.fc_ineligible_reason_count[EXT4_FC_COMMIT_FAILED]++;
reason = EXT4_FC_REASON_FC_FAILED;
goto out;
status = EXT4_FC_STATUS_FAILED;
goto fallback;
}
atomic_inc(&sbi->s_fc_subtid);
jbd2_fc_end_commit(journal);
out:
spin_lock(&sbi->s_fc_lock);
if (reason != EXT4_FC_REASON_OK &&
reason != EXT4_FC_REASON_ALREADY_COMMITTED) {
sbi->s_fc_stats.fc_ineligible_commits++;
} else {
sbi->s_fc_stats.fc_num_commits++;
sbi->s_fc_stats.fc_numblks += nblks;
}
spin_unlock(&sbi->s_fc_lock);
nblks = (reason == EXT4_FC_REASON_OK) ? nblks : 0;
trace_ext4_fc_commit_stop(sb, nblks, reason);
commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
ret = jbd2_fc_end_commit(journal);
/*
* weight the commit time higher than the average time so we don't
* react too strongly to vast changes in the commit time
* weight the commit time higher than the average time so we
* don't react too strongly to vast changes in the commit time
*/
if (likely(sbi->s_fc_avg_commit_time))
sbi->s_fc_avg_commit_time = (commit_time +
sbi->s_fc_avg_commit_time * 3) / 4;
else
sbi->s_fc_avg_commit_time = commit_time;
jbd_debug(1,
"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);
if (reason == EXT4_FC_REASON_FC_START_FAILED ||
reason == EXT4_FC_REASON_INELIGIBLE)
return jbd2_complete_transaction(journal, commit_tid);
return 0;
commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
ext4_fc_update_stats(sb, status, commit_time, nblks);
return ret;

fallback:
ret = jbd2_fc_end_commit_fallback(journal);
ext4_fc_update_stats(sb, status, 0, 0);
return ret;
}

/*
Expand Down Expand Up @@ -2132,7 +2141,7 @@ int ext4_fc_info_show(struct seq_file *seq, void *v)
"fc stats:\n%ld commits\n%ld ineligible\n%ld numblks\n%lluus avg_commit_time\n",
stats->fc_num_commits, stats->fc_ineligible_commits,
stats->fc_numblks,
div_u64(sbi->s_fc_avg_commit_time, 1000));
div_u64(stats->s_fc_avg_commit_time, 1000));
seq_puts(seq, "Ineligible reasons:\n");
for (i = 0; i < EXT4_FC_REASON_MAX; i++)
seq_printf(seq, "\"%s\":\t%d\n", fc_ineligible_reasons[i],
Expand Down
27 changes: 14 additions & 13 deletions fs/ext4/fast_commit.h
Expand Up @@ -71,21 +71,19 @@ struct ext4_fc_tail {
};

/*
* Fast commit reason codes
* Fast commit status codes
*/
enum {
EXT4_FC_STATUS_OK = 0,
EXT4_FC_STATUS_INELIGIBLE,
EXT4_FC_STATUS_SKIPPED,
EXT4_FC_STATUS_FAILED,
};

/*
* Fast commit ineligiblity reasons:
*/
enum {
/*
* Commit status codes:
*/
EXT4_FC_REASON_OK = 0,
EXT4_FC_REASON_INELIGIBLE,
EXT4_FC_REASON_ALREADY_COMMITTED,
EXT4_FC_REASON_FC_START_FAILED,
EXT4_FC_REASON_FC_FAILED,

/*
* Fast commit ineligiblity reasons:
*/
EXT4_FC_REASON_XATTR = 0,
EXT4_FC_REASON_CROSS_RENAME,
EXT4_FC_REASON_JOURNAL_FLAG_CHANGE,
Expand Down Expand Up @@ -117,7 +115,10 @@ struct ext4_fc_stats {
unsigned int fc_ineligible_reason_count[EXT4_FC_REASON_MAX];
unsigned long fc_num_commits;
unsigned long fc_ineligible_commits;
unsigned long fc_failed_commits;
unsigned long fc_skipped_commits;
unsigned long fc_numblks;
u64 s_fc_avg_commit_time;
};

#define EXT4_FC_REPLAY_REALLOC_INCREMENT 4
Expand Down

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