pnfs: Proper delay for NFS4ERR_RECALLCONFLICT in layout_get_done

An NFS4ERR_RECALLCONFLICT is returned by server from a GET_LAYOUT
only when a Server Sent a RECALL do to that GET_LAYOUT, or
the RECALL and GET_LAYOUT crossed on the wire.
In any way this means we want to wait at most until in-flight IO
is finished and the RECALL can be satisfied.

So a proper wait here is more like 1/10 of a second, not 15 seconds
like we have now. In case of a server bug we delay exponentially
longer on each retry.

Current code totally craps out performance of very large files on
most pnfs-objects layouts, because of how the map changes when the
file has grown into the next raid group.

[Stable: This will patch back to 3.9. If there are earlier still
 maintained trees, please tell me I'll send a patch]

CC: Stable Tree <stable@vger.kernel.org>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index a9eaaaa..a196532 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7409,9 +7409,9 @@ static void nfs4_layoutget_done(struct rpc_task *task, void *calldata)
        struct nfs_server *server = NFS_SERVER(inode);
        struct pnfs_layout_hdr *lo;
        struct nfs4_state *state = NULL;
-       unsigned long timeo, giveup;
+       unsigned long timeo, now, giveup;
 
-       dprintk("--> %s\n", __func__);
+       dprintk("--> %s tk_status => %d\n", __func__, -task->tk_status);
 
        if (!nfs41_sequence_done(task, &lgp->res.seq_res))
                goto out;
@@ -7419,12 +7419,38 @@ static void nfs4_layoutget_done(struct rpc_task *task, void *calldata)
        switch (task->tk_status) {
        case 0:
                goto out;
+       /*
+        * NFS4ERR_LAYOUTTRYLATER is a conflict with another client
+        * (or clients) writing to the same RAID stripe
+        */
        case -NFS4ERR_LAYOUTTRYLATER:
+       /*
+        * NFS4ERR_RECALLCONFLICT is when conflict with self (must recall
+        * existing layout before getting a new one).
+        */
        case -NFS4ERR_RECALLCONFLICT:
                timeo = rpc_get_timeout(task->tk_client);
                giveup = lgp->args.timestamp + timeo;
-               if (time_after(giveup, jiffies))
-                       task->tk_status = -NFS4ERR_DELAY;
+               now = jiffies;
+               if (time_after(giveup, now)) {
+                       unsigned long delay;
+
+                       /* Delay for:
+                        * - Not less then NFS4_POLL_RETRY_MIN.
+                        * - One last time a jiffie before we give up
+                        * - exponential backoff (time_now minus start_attempt)
+                        */
+                       delay = max_t(unsigned long, NFS4_POLL_RETRY_MIN,
+                                   min((giveup - now - 1),
+                                       now - lgp->args.timestamp));
+
+                       dprintk("%s: NFS4ERR_RECALLCONFLICT waiting %lu\n",
+                               __func__, delay);
+                       rpc_delay(task, delay);
+                       task->tk_status = 0;
+                       rpc_restart_call_prepare(task);
+                       goto out; /* Do not call nfs4_async_handle_error() */
+               }
                break;
        case -NFS4ERR_EXPIRED:
        case -NFS4ERR_BAD_STATEID: