NFSv4: Ensure that we recover from the OPEN + OPEN_CONFIRM BAD_STATEID race

 If the server is in the unconfirmed OPEN state for a given open owner
 and receives a second OPEN for the same open owner, it will cancel the
 state of the first request and set up an OPEN_CONFIRM for the second.

 This can cause a race that is discussed in rfc3530 on page 181.

 The following patch allows the client to recover by retrying the
 original open request.

 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index a8be9af610a..ff378126ccd 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -785,6 +785,16 @@ static struct nfs4_state *nfs4_do_open(struct inode *dir, struct dentry *dentry,
                         exception.retry = 1;
                         continue;
                 }
+                /*
+                 * BAD_STATEID on OPEN means that the server cancelled our
+                 * state before it received the OPEN_CONFIRM.
+                 * Recover by retrying the request as per the discussion
+                 * on Page 181 of RFC3530.
+                 */
+                if (status == -NFS4ERR_BAD_STATEID) {
+                        exception.retry = 1;
+                        continue;
+                }
                 res = ERR_PTR(nfs4_handle_exception(NFS_SERVER(dir),
                                         status, &exception));
         } while (exception.retry);