Skip to content
Commit 2b5e0276 authored by Vivek Goyal's avatar Vivek Goyal Committed by Greg Kroah-Hartman
Browse files

virtiofs: schedule blocking async replies in separate worker



[ Upstream commit bb737bbe ]

In virtiofs (unlike in regular fuse) processing of async replies is
serialized.  This can result in a deadlock in rare corner cases when
there's a circular dependency between the completion of two or more async
replies.

Such a deadlock can be reproduced with xfstests:generic/503 if TEST_DIR ==
SCRATCH_MNT (which is a misconfiguration):

 - Process A is waiting for page lock in worker thread context and blocked
   (virtio_fs_requests_done_work()).
 - Process B is holding page lock and waiting for pending writes to
   finish (fuse_wait_on_page_writeback()).
 - Write requests are waiting in virtqueue and can't complete because
   worker thread is blocked on page lock (process A).

Fix this by creating a unique work_struct for each async reply that can
block (O_DIRECT read).

Fixes: a62a8ef9 ("virtio-fs: add virtiofs filesystem")
Signed-off-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent ff86bd6c
Loading
Loading
Loading
Loading
0% Loading or .
You are about to add 0 people to the discussion. Proceed with caution.
Please register or to comment