On Thu 22-09-22 11:15:42, Jan Kara wrote:
On Wed 21-09-22 22:52:34, Theodore Ts'o wrote:
On Thu, 8 Sep 2022 11:21:24 +0200, Jan Kara wrote:
One of the side-effects of mb_optimize_scan was that the optimized functions to select next group to try were called even before we tried the goal group. As a result we no longer allocate files close to corresponding inodes as well as we don't try to expand currently allocated extent in the same group. This results in reaim regression with workfile.disk workload of upto 8% with many clients on my test machine:
[...]
Applied, thanks!
[1/5] ext4: Make mballoc try target group first even with mb_optimize_scan commit: 4fca50d440cc5d4dc570ad5484cc0b70b381bc2a [2/5] ext4: Avoid unnecessary spreading of allocations among groups commit: 1940265ede6683f6317cba0d428ce6505eaca944 [3/5] ext4: Make directory inode spreading reflect flexbg size commit: 613c5a85898d1cd44e68f28d65eccf64a8ace9cf [4/5] ext4: Use locality group preallocation for small closed files commit: a9f2a2931d0e197ab28c6007966053fdababd53f [5/5] ext4: Use buckets for cr 1 block scan instead of rbtree commit: 83e80a6e3543f37f74c8e48a5f305b054b65ce2a
Thanks Ted! I just have locally a small fixup to the series that was reported by Smatch. It is attached, either fold it into the last patch or just merge it as a separate patch. Thanks!
Ted, I've noticed you've merged my mballoc fixes (and pushed them to Linus) without this fixup. Can you please merge it? The use of uninitialized variable seems rare but possible...
Honza
From 8885b11fb253e08ecfa90a28beffb01719af84f5 Mon Sep 17 00:00:00 2001 From: Jan Kara jack@suse.cz Date: Thu, 22 Sep 2022 11:09:29 +0200 Subject: [PATCH] ext4: Fixup possible uninitialized variable access in ext4_mb_choose_next_group_cr1()
Variable 'grp' may be left uninitialized if there's no group with suitable average fragment size (or larger). Fix the problem by initializing it earlier.
Fixes: 83e80a6e3543 ("ext4: use buckets for cr 1 block scan instead of rbtree") Reported-by: Dan Carpenter dan.carpenter@oracle.com Signed-off-by: Jan Kara jack@suse.cz
fs/ext4/mballoc.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 71f5b67d7f28..9dad93059945 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -910,7 +910,7 @@ static void ext4_mb_choose_next_group_cr1(struct ext4_allocation_context *ac, int *new_cr, ext4_group_t *group, ext4_group_t ngroups) { struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
- struct ext4_group_info *grp, *iter;
- struct ext4_group_info *grp = NULL, *iter; int i;
if (unlikely(ac->ac_flags & EXT4_MB_CR1_OPTIMIZED)) { @@ -927,7 +927,6 @@ static void ext4_mb_choose_next_group_cr1(struct ext4_allocation_context *ac, read_unlock(&sbi->s_mb_avg_fragment_size_locks[i]); continue; }
grp = NULL;-- 2.35.3