[PATCH 5.19 0265/1157] erofs: wake up all waiters after z_erofs_lzma_head ready

Greg Kroah-Hartman
2022-08-15T23:01:58Z

From: Yuwen Chen <chenyuwen1@meizu.com>

[ Upstream commit 2df7c4bd7c1d2bc5ece5e9ed19dbd386810c2a65 ]

When the user mounts the erofs second times, the decompression thread
may hung. The problem happens due to a sequence of steps like the
following:

1) Task A called z_erofs_load_lzma_config which obtain all of the node
from the z_erofs_lzma_head.

2) At this time, task B called the z_erofs_lzma_decompress and wanted to
get a node. But the z_erofs_lzma_head was empty, the Task B had to
sleep.

3) Task A release nodes and push nodes into the z_erofs_lzma_head. But
task B was still sleeping.

One example report when the hung happens:
task:kworker/u3:1 state:D stack:14384 pid: 86 ppid: 2 flags:0x00004000
Workqueue: erofs_unzipd z_erofs_decompressqueue_work
Call Trace:
<TASK>
__schedule+0x281/0x760
schedule+0x49/0xb0
z_erofs_lzma_decompress+0x4bc/0x580
? cpu_core_flags+0x10/0x10
z_erofs_decompress_pcluster+0x49b/0xba0
? __update_load_avg_se+0x2b0/0x330
? __update_load_avg_se+0x2b0/0x330
? update_load_avg+0x5f/0x690
? update_load_avg+0x5f/0x690
? set_next_entity+0xbd/0x110
? _raw_spin_unlock+0xd/0x20
z_erofs_decompress_queue.isra.0+0x2e/0x50
z_erofs_decompressqueue_work+0x30/0x60
process_one_work+0x1d3/0x3a0
worker_thread+0x45/0x3a0
? process_one_work+0x3a0/0x3a0
kthread+0xe2/0x110
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x22/0x30
</TASK>

Signed-off-by: Yuwen Chen <chenyuwen1@meizu.com>
Fixes: 622ceaddb764 ("erofs: lzma compression support")
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220626224041.4288-1-chenyuwen1@meizu.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/erofs/decompressor_lzma.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/erofs/decompressor_lzma.c b/fs/erofs/decompressor_lzma.c
index 05a3063cf2bc..5e59b3f523eb 100644
--- a/fs/erofs/decompressor_lzma.c
+++ b/fs/erofs/decompressor_lzma.c
@@ -143,6 +143,7 @@ int z_erofs_load_lzma_config(struct super_block *sb,
DBG_BUGON(z_erofs_lzma_head);
z_erofs_lzma_head = head;
spin_unlock(&z_erofs_lzma_lock);
+ wake_up_all(&z_erofs_lzma_wq);

z_erofs_lzma_max_dictsize = dict_size;
mutex_unlock(&lzma_resize_mutex);
--
2.35.1