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| author | Huang Jianan <huangjianan@oppo.com> | 2021-11-18 16:58:44 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-12-01 11:04:50 +0300 |
| commit | 4339cd0825946b6695a7c403dd48df14e9f66512 (patch) | |
| tree | 1dcb671adbb40290912bf4ecc1ebdbc52101938b /fs/erofs | |
| parent | 8b3b9aaada48297d4a1b10b248cbace3c973601e (diff) | |
| download | linux-4339cd0825946b6695a7c403dd48df14e9f66512.tar.xz | |
erofs: fix deadlock when shrink erofs slab
[ Upstream commit 57bbeacdbee72a54eb97d56b876cf9c94059fc34 ]
We observed the following deadlock in the stress test under low
memory scenario:
Thread A Thread B
- erofs_shrink_scan
- erofs_try_to_release_workgroup
- erofs_workgroup_try_to_freeze -- A
- z_erofs_do_read_page
- z_erofs_collection_begin
- z_erofs_register_collection
- erofs_insert_workgroup
- xa_lock(&sbi->managed_pslots) -- B
- erofs_workgroup_get
- erofs_wait_on_workgroup_freezed -- A
- xa_erase
- xa_lock(&sbi->managed_pslots) -- B
To fix this, it needs to hold xa_lock before freezing the workgroup
since xarray will be touched then. So let's hold the lock before
accessing each workgroup, just like what we did with the radix tree
before.
[ Gao Xiang: Jianhua Hao also reports this issue at
https://lore.kernel.org/r/b10b85df30694bac8aadfe43537c897a@xiaomi.com ]
Link: https://lore.kernel.org/r/20211118135844.3559-1-huangjianan@oppo.com
Fixes: 64094a04414f ("erofs: convert workstn to XArray")
Reviewed-by: Chao Yu <chao@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Reported-by: Jianhua Hao <haojianhua1@xiaomi.com>
Signed-off-by: Gao Xiang <xiang@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'fs/erofs')
| -rw-r--r-- | fs/erofs/utils.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/fs/erofs/utils.c b/fs/erofs/utils.c index bd86067a63f7..3ca703cd5b24 100644 --- a/fs/erofs/utils.c +++ b/fs/erofs/utils.c @@ -141,7 +141,7 @@ static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi, * however in order to avoid some race conditions, add a * DBG_BUGON to observe this in advance. */ - DBG_BUGON(xa_erase(&sbi->managed_pslots, grp->index) != grp); + DBG_BUGON(__xa_erase(&sbi->managed_pslots, grp->index) != grp); /* last refcount should be connected with its managed pslot. */ erofs_workgroup_unfreeze(grp, 0); @@ -156,15 +156,19 @@ static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi, unsigned int freed = 0; unsigned long index; + xa_lock(&sbi->managed_pslots); xa_for_each(&sbi->managed_pslots, index, grp) { /* try to shrink each valid workgroup */ if (!erofs_try_to_release_workgroup(sbi, grp)) continue; + xa_unlock(&sbi->managed_pslots); ++freed; if (!--nr_shrink) - break; + return freed; + xa_lock(&sbi->managed_pslots); } + xa_unlock(&sbi->managed_pslots); return freed; } |