From ef1820f9be27b6ad158f433ab38002ab8131db4d Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Wed, 4 Sep 2013 17:04:49 +1000 Subject: NFSv4: Don't try to recover NFSv4 locks when they are lost. When an NFSv4 client loses contact with the server it can lose any locks that it holds. Currently when it reconnects to the server it simply tries to reclaim those locks. This might succeed even though some other client has held and released a lock in the mean time. So the first client might think the file is unchanged, but it isn't. This isn't good. If, when recovery happens, the locks cannot be claimed because some other client still holds the lock, then we get a message in the kernel logs, but the client can still write. So two clients can both think they have a lock and can both write at the same time. This is equally not good. There was a patch a while ago http://comments.gmane.org/gmane.linux.nfs/41917 which tried to address some of this, but it didn't seem to go anywhere. That patch would also send a signal to the process. That might be useful but for now this patch just causes writes to fail. For NFSv4 (unlike v2/v3) there is a strong link between the lock and the write request so we can fairly easily fail any IO of the lock is gone. While some applications might not expect this, it is still safer than allowing the write to succeed. Because this is a fairly big change in behaviour a module parameter, "recover_locks", is introduced which defaults to true (the current behaviour) but can be set to "false" to tell the client not to try to recover things that were lost. Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust --- fs/nfs/proc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'fs/nfs/proc.c') diff --git a/fs/nfs/proc.c b/fs/nfs/proc.c index c041c41f7a52..a8f57c728df5 100644 --- a/fs/nfs/proc.c +++ b/fs/nfs/proc.c @@ -623,9 +623,10 @@ static void nfs_proc_read_setup(struct nfs_read_data *data, struct rpc_message * msg->rpc_proc = &nfs_procedures[NFSPROC_READ]; } -static void nfs_proc_read_rpc_prepare(struct rpc_task *task, struct nfs_read_data *data) +static int nfs_proc_read_rpc_prepare(struct rpc_task *task, struct nfs_read_data *data) { rpc_call_start(task); + return 0; } static int nfs_write_done(struct rpc_task *task, struct nfs_write_data *data) @@ -644,9 +645,10 @@ static void nfs_proc_write_setup(struct nfs_write_data *data, struct rpc_message msg->rpc_proc = &nfs_procedures[NFSPROC_WRITE]; } -static void nfs_proc_write_rpc_prepare(struct rpc_task *task, struct nfs_write_data *data) +static int nfs_proc_write_rpc_prepare(struct rpc_task *task, struct nfs_write_data *data) { rpc_call_start(task); + return 0; } static void nfs_proc_commit_rpc_prepare(struct rpc_task *task, struct nfs_commit_data *data) -- cgit v1.2.3