linux-ext4 - [PATCH v2 13/20] ext4: remove ac->ac_found > sbi->s_mb_min_to_scan dead check in ext4_mb_check

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Message-Id: <20230228114306.3328235-14-shikemeng@huaweicloud.com>
Date:   Tue, 28 Feb 2023 19:42:59 +0800
From:   Kemeng Shi <shikemeng@...weicloud.com>
To:     tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz,
        ojaswin@...ux.ibm.com, ritesh.list@...il.com
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        shikemeng@...weicloud.com
Subject: [PATCH v2 13/20] ext4: remove ac->ac_found > sbi->s_mb_min_to_scan dead check in ext4_mb_check_limits

Only call trace of ext4_mb_check_limits is as following:
ext4_mb_complex_scan_group
	ext4_mb_measure_extent
		ext4_mb_check_limits(ac, e4b, 0);
	ext4_mb_check_limits(ac, e4b, 1);

If the first ac->ac_found > sbi->s_mb_max_to_scan check in
ext4_mb_check_limits is met, we will set ac_status to
AC_STATUS_BREAK and call ext4_mb_try_best_found to try to use
ac->ac_b_ex.
If ext4_mb_try_best_found successes, then block allocation finishs,
the removed ac->ac_found > sbi->s_mb_min_to_scan check is not reachable.
If ext4_mb_try_best_found fails, then we set EXT4_MB_HINT_FIRST and
reset ac->ac_b_ex to retry block allocation. We will use any found
free extent in ext4_mb_measure_extent before reach the removed
ac->ac_found > sbi->s_mb_min_to_scan check.
In summary, the removed ac->ac_found > sbi->s_mb_min_to_scan check is
not reachable and we can remove that dead check.

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
---
 fs/ext4/mballoc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index f40af7430fca..07a840e8543c 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2039,8 +2039,7 @@ static void ext4_mb_check_limits(struct ext4_allocation_context *ac,
 	if (bex->fe_len < gex->fe_len)
 		return;

-	if ((finish_group || ac->ac_found > sbi->s_mb_min_to_scan)
-			&& bex->fe_group == e4b->bd_group) {
+	if (finish_group && bex->fe_group == e4b->bd_group) {
 		/* recheck chunk's availability - we don't know
 		 * when it was found (within this lock-unlock
 		 * period or not) */
-- 
2.30.0