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authorHuang Jianan <huangjianan@oppo.com>2021-11-18 21:58:44 +0800
committerGao Xiang <xiang@kernel.org>2021-11-23 14:58:16 +0800
commit57bbeacdbee72a54eb97d56b876cf9c94059fc34 (patch)
tree3ac13afe34eff1fb973ab3c07a08147f3a3f2c9d /fs
parent136057256686de39cc3a07c2e39ef6bc43003ff6 (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')
-rw-r--r--fs/erofs/utils.c8
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;
}