[RFC 08/11] ext4: Don't skip prefetching BLOCK_UNINIT groups
From: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Date: 2023-01-27 12:39:18
Also in:
linux-fsdevel, lkml
Subsystem:
ext4 file system, filesystems (vfs and infrastructure), the rest · Maintainers:
"Theodore Ts'o", Alexander Viro, Christian Brauner, Linus Torvalds
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 <ojaswin@linux.ibm.com> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> --- 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 14529d2fe65f..48726a831264 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c@@ -2557,9 +2557,7 @@ ext4_group_t ext4_mb_prefetch(struct super_block *sb, ext4_group_t group, */ if (!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)
@@ -2600,9 +2598,7 @@ void ext4_mb_prefetch_fini(struct super_block *sb, ext4_group_t group, grp = ext4_get_group_info(sb, group); if (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; }
--
2.31.1