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 <[email protected]>
Reviewed-by: Ojaswin Mujoo <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 591bd8e5e5c7be90c223f2fb9200600a4d2fc351..eeafa1bba8246509539553bc5337b45abe743c39 100644 (file)
--- 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) */