NFSv4: Resend the READ/WRITE RPC call if a stateid change causes an error

Adds logic to ensure that if the server returns a BAD_STATEID,
or other state related error, then we check if the stateid has
already changed. If it has, then rather than start state recovery,
we should just resend the failed RPC call with the new stateid.

Allow nfs4_select_rw_stateid to notify that the stateid is unstable by
having it return -EWOULDBLOCK if an RPC is underway that might change the
stateid.

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

1 files changed, 23 insertions, 9 deletions

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 8db102c7add6..4e95bd72f480 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -989,13 +989,14 @@ int nfs4_set_lock_state(struct nfs4_state *state, struct file_lock *fl)
         return 0;
 }
 
-static bool nfs4_copy_lock_stateid(nfs4_stateid *dst, struct nfs4_state *state,
+static int nfs4_copy_lock_stateid(nfs4_stateid *dst,
+                struct nfs4_state *state,
                 const struct nfs_lockowner *lockowner)
 {
         struct nfs4_lock_state *lsp;
         fl_owner_t fl_owner;
         pid_t fl_pid;
-        bool ret = false;
+        int ret = -ENOENT;
 
 
         if (lockowner == NULL)
@@ -1010,7 +1011,10 @@ static bool nfs4_copy_lock_stateid(nfs4_stateid *dst, struct nfs4_state *state,
         lsp = __nfs4_find_lock_state(state, fl_owner, fl_pid, NFS4_ANY_LOCK_TYPE);
         if (lsp != NULL && test_bit(NFS_LOCK_INITIALIZED, &lsp->ls_flags) != 0) {
                 nfs4_stateid_copy(dst, &lsp->ls_stateid);
-                ret = true;
+                ret = 0;
+                smp_rmb();
+                if (!list_empty(&lsp->ls_seqid.list))
+                        ret = -EWOULDBLOCK;
         }
         spin_unlock(&state->state_lock);
         nfs4_put_lock_state(lsp);
@@ -1018,28 +1022,38 @@ out:
         return ret;
 }
 
-static void nfs4_copy_open_stateid(nfs4_stateid *dst, struct nfs4_state *state)
+static int nfs4_copy_open_stateid(nfs4_stateid *dst, struct nfs4_state *state)
 {
+        int ret;
         int seq;
 
         do {
                 seq = read_seqbegin(&state->seqlock);
                 nfs4_stateid_copy(dst, &state->stateid);
+                ret = 0;
+                smp_rmb();
+                if (!list_empty(&state->owner->so_seqid.list))
+                        ret = -EWOULDBLOCK;
         } while (read_seqretry(&state->seqlock, seq));
+        return ret;
 }
 
 /*
  * Byte-range lock aware utility to initialize the stateid of read/write
  * requests.
  */
-void nfs4_select_rw_stateid(nfs4_stateid *dst, struct nfs4_state *state,
+int nfs4_select_rw_stateid(nfs4_stateid *dst, struct nfs4_state *state,
                 fmode_t fmode, const struct nfs_lockowner *lockowner)
 {
+        int ret = 0;
         if (nfs4_copy_delegation_stateid(dst, state->inode, fmode))
-                return;
-        if (nfs4_copy_lock_stateid(dst, state, lockowner))
-                return;
-        nfs4_copy_open_stateid(dst, state);
+                goto out;
+        ret = nfs4_copy_lock_stateid(dst, state, lockowner);
+        if (ret != -ENOENT)
+                goto out;
+        ret = nfs4_copy_open_stateid(dst, state);
+out:
+        return ret;
 }
 
 struct nfs_seqid *nfs_alloc_seqid(struct nfs_seqid_counter *counter, gfp_t gfp_mask)