diff options
author | Huang Jianan <huangjianan@oppo.com> | 2021-11-18 16:58:44 +0300 |
---|---|---|
committer | Gao Xiang <xiang@kernel.org> | 2021-11-23 09:58:16 +0300 |
commit | 57bbeacdbee72a54eb97d56b876cf9c94059fc34 (patch) | |
tree | 3ac13afe34eff1fb973ab3c07a08147f3a3f2c9d /fs/erofs | |
parent | 136057256686de39cc3a07c2e39ef6bc43003ff6 (diff) |
erofs: fix deadlock when shrink erofs slab
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>
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 84da2c280012..ec9a1d780dc1 100644 --- a/fs/erofs/utils.c +++ b/fs/erofs/utils.c @@ -150,7 +150,7 @@ 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); @@ -165,15 +165,19 @@ 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; } |