From 3c6296046c85333bc52555a670a9093d9e2657bb Mon Sep 17 00:00:00 2001 From: Ojaswin Mujoo Date: Tue, 30 May 2023 18:03:46 +0530 Subject: [PATCH] ext4: Don't skip prefetching BLOCK_UNINIT groups Currently, ext4_mb_prefetch() and ext4_mb_prefetch_fini() skip BLOCK_UNINIT groups since fetching their bitmaps doesn't need disk IO. As a consequence, we end not initializing the buddy structures and CR0/1 lists for these BGs, even though it can be done without any disk IO overhead. Hence, don't skip such BGs during prefetch and prefetch_fini. This improves the accuracy of CR0/1 allocation as earlier, we could have essentially empty BLOCK_UNINIT groups being ignored by CR0/1 due to their buddy not being initialized, leading to slower CR2 allocations. With this patch CR0/1 will be able to discover these groups as well, thus improving performance. Signed-off-by: Ojaswin Mujoo Reviewed-by: Ritesh Harjani (IBM) Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/dc3130b8daf45ffe63d8a3c1edcf00eb8ba70e1f.1685449706.git.ojaswin@linux.ibm.com Signed-off-by: Theodore Ts'o --- fs/ext4/mballoc.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 704f8e5..fb9780b 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2589,9 +2589,7 @@ ext4_group_t ext4_mb_prefetch(struct super_block *sb, ext4_group_t group, */ if (gdp && grp && !EXT4_MB_GRP_TEST_AND_SET_READ(grp) && EXT4_MB_GRP_NEED_INIT(grp) && - ext4_free_group_clusters(sb, gdp) > 0 && - !(ext4_has_group_desc_csum(sb) && - (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)))) { + ext4_free_group_clusters(sb, gdp) > 0 ) { bh = ext4_read_block_bitmap_nowait(sb, group, true); if (bh && !IS_ERR(bh)) { if (!buffer_uptodate(bh) && cnt) @@ -2632,9 +2630,7 @@ void ext4_mb_prefetch_fini(struct super_block *sb, ext4_group_t group, grp = ext4_get_group_info(sb, group); if (grp && gdp && EXT4_MB_GRP_NEED_INIT(grp) && - ext4_free_group_clusters(sb, gdp) > 0 && - !(ext4_has_group_desc_csum(sb) && - (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)))) { + ext4_free_group_clusters(sb, gdp) > 0) { if (ext4_mb_init_group(sb, group, GFP_NOFS)) break; } -- 2.7.4