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authorZhang Xiaoxu <zhangxiaoxu5@huawei.com>2021-06-26 15:50:41 +0800
committerTrond Myklebust <trond.myklebust@hammerspace.com>2021-06-28 09:34:39 -0400
commitfcb170a9d825d7db4a3fb870b0300f5a40a8d096 (patch)
tree171c63b1fab9dc492a643c6142c96b230492bae2 /net/sunrpc
parentb42ad64f5f216db05310783cbded56176c3a09df (diff)
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>
Diffstat (limited to 'net/sunrpc')
-rw-r--r--net/sunrpc/sched.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 39ed0e0afe6d..71993adb0762 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -595,7 +595,8 @@ static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *q
* Service a batch of tasks from a single owner.
*/
q = &queue->tasks[queue->priority];
- if (!list_empty(q) && --queue->nr) {
+ if (!list_empty(q) && queue->nr) {
+ queue->nr--;
task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
goto out;
}