Huang Jianan 4339cd0825 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>
2021-12-01 09:04:50 +01:00
..
2021-10-07 11:20:08 -07:00
2021-08-19 09:02:55 +09:00
2021-04-12 15:04:29 +02:00
2021-09-02 12:32:12 -07:00
2021-11-18 19:16:19 +01:00
2021-08-26 22:28:02 +02:00
2021-11-18 19:16:48 +01:00
2021-09-22 09:21:02 -07:00
2021-09-10 09:46:48 -07:00
2021-06-29 10:53:48 -07:00
2021-09-03 15:33:47 -07:00
2021-08-16 10:50:32 -06:00
2021-11-25 09:48:46 +01:00
2021-08-19 09:02:55 +09:00
2021-09-09 11:39:57 -07:00
\n
2021-08-30 10:24:50 -07:00
2021-11-25 09:48:46 +01:00
2021-08-31 11:13:35 -07:00
2021-09-09 13:25:49 -07:00
2021-09-11 14:48:42 -07:00
2021-11-25 09:49:08 +01:00
2021-08-31 11:06:32 -07:00
2021-06-29 10:53:48 -07:00
2021-08-18 22:08:24 +02:00
2021-08-10 17:57:22 +02:00