Viewing: ext4-not-skip-prefetching-BLOCK_UNINIT-groups.patch
commit 3c6296046c85333bc52555a670a9093d9e2657bb
Author: Ojaswin Mujoo <ojaswin@linux.ibm.com>
AuthorDate: Tue May 30 18:03:46 2023 +0530
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 <ojaswin@linux.ibm.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/dc3130b8daf45ffe63d8a3c1edcf00eb8ba70e1f.1685449706.git.ojaswin@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
Index: linux-stage/fs/ext4/mballoc.c
===================================================================
--- linux-stage.orig/fs/ext4/mballoc.c
+++ linux-stage/fs/ext4/mballoc.c
@@ -2580,9 +2580,7 @@ ext4_group_t ext4_mb_prefetch(struct sup
*/
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, 1);
if (bh && !IS_ERR(bh)) {
if (!buffer_uptodate(bh) && cnt)
@@ -2613,20 +2611,18 @@ ext4_group_t ext4_mb_prefetch(struct sup
void ext4_mb_prefetch_fini(struct super_block *sb, ext4_group_t group,
unsigned int nr)
{
- while (nr-- > 0) {
- struct ext4_group_desc *gdp = ext4_get_group_desc(sb, group,
- NULL);
- struct ext4_group_info *grp = ext4_get_group_info(sb, group);
+ struct ext4_group_desc *gdp;
+ struct ext4_group_info *grp;
+ while (nr-- > 0) {
if (!group)
group = ext4_get_groups_count(sb);
group--;
+ gdp = ext4_get_group_desc(sb, group, NULL);
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;
}
