From:   Vasily Averin <vvs@virtuozzo.com>
Subject: [PATCH] nfs4: handle async processing of F_SETLK with FL_SLEEP
To:     Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>
Cc:     kernel@openvz.org, linux-nfs@vger.kernel.org,
        linux-kernel@vger.kernel.org
Message-ID: <3a2c6cb9-abe7-ab32-b11c-d78621361555@virtuozzo.com>
Date:   Mon, 27 Dec 2021 13:45:45 +0300
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nfsd and lockd use F_SETLK cmd with the FL_SLEEP flag set to request
asynchronous processing of blocking locks.

Currently nfs4 use locks_lock_inode_wait() function blocked on such requests.
To handle such requests properly, non-blocking posix_file_lock()
function should be used instead.

https://bugzilla.kernel.org/show_bug.cgi?id=215383
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
---
VvS: I'm not sure that request->fl_file points to the same state->inode
used in locks_lock_inode_wait(). If it is not, posix_lock_inode() can be
used here, but this function is static currently and should be exported first.
---
 fs/nfs/nfs4proc.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index ee3bc79f6ca3..54431b296c85 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7200,8 +7200,11 @@ static int _nfs4_proc_setlk(struct nfs4_state *state, int cmd, struct file_lock
 	int status;
 
 	request->fl_flags |= FL_ACCESS;
-	status = locks_lock_inode_wait(state->inode, request);
-	if (status < 0)
+	if ((request->fl_flags && FL_SLEEP) && IS_SETLK(cmd))
+		status = posix_lock_file(request->fl_file, request, NULL);
+	else
+		status = locks_lock_inode_wait(state->inode, request);
+	if (status)
 		goto out;
 	mutex_lock(&sp->so_delegreturn_mutex);
 	down_read(&nfsi->rwsem);
-- 
2.25.1