Zhang Xiaoxu fcb170a9d8 SUNRPC: Fix the batch tasks count wraparound.
The 'queue->nr' will wraparound from 0 to 255 when only current
priority queue has tasks. This maybe lead a deadlock same as commit
dfe1fe75e00e ("NFSv4: Fix deadlock between nfs4_evict_inode()
and nfs4_opendata_get_inode()"):

Privileged delegreturn task is queued to privileged list because all
the slots are assigned. When non-privileged task complete and release
the slot, a non-privileged maybe picked out. It maybe allocate slot
failed when the session on draining.

If the 'queue->nr' has wraparound to 255, and no enough slot to
service it, then the privileged delegreturn will lost to wake up.

So we should avoid the wraparound on 'queue->nr'.

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 5fcdfacc01f3 ("NFSv4: Return delegations synchronously in evict_inode")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
2021-06-28 09:34:39 -04:00
..
2021-05-27 08:46:19 -04:00
2020-12-09 09:38:34 -05:00
2018-12-19 13:52:46 -05:00
2020-03-16 12:04:33 -04:00