From 9c97c34a998a01bc0cf970b1685456bc2ea16b64 Mon Sep 17 00:00:00 2001 From: Kemeng Shi Date: Wed, 24 Apr 2024 14:19:00 +0800 Subject: [PATCH] ext4: keep "prefetch_grp" and "nr" consistent Keep "prefetch_grp" and "nr" consistent to avoid to call ext4_mb_prefetch_fini with non-prefetched groups. When we step into next criteria, "prefetch_grp" is set to prefetch start of new criteria while "nr" is number of the prefetched group in previous criteria. If previous criteria and next criteria are both inexpensive (< CR_GOAL_LEN_SLOW) and prefetch_ios reachs sbi->s_mb_prefetch_limit in previous criteria, "prefetch_grp" and "nr" will be inconsistent and may introduce unexpected cost to do ext4_mb_init_group for non-prefetched groups. Reset "nr" to 0 when we reset "prefetch_grp" to goal group to keep them consistent. Signed-off-by: Kemeng Shi Reviewed-by: Ojaswin Mujoo Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20240424061904.987525-2-shikemeng@huaweicloud.com Signed-off-by: Theodore Ts'o --- fs/ext4/mballoc.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index c65fac9b8c72f..33e6a3ebdb55f 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2860,6 +2860,7 @@ repeat: group = ac->ac_g_ex.fe_group; ac->ac_groups_linear_remaining = sbi->s_mb_max_linear_groups; prefetch_grp = group; + nr = 0; for (i = 0, new_cr = cr; i < ngroups; i++, ext4_mb_choose_next_group(ac, &new_cr, &group, ngroups)) { -- 2.47.2