pnfs: lift retry logic from send_layoutget to pnfs_update_layout

If we get back something like NFS4ERR_OLD_STATEID, that will be
translated into -EAGAIN, and the do/while loop in send_layoutget
will drive the call again.

This is not quite what we want, I think. An error like that is a
sign that something has changed. That something could have been a
concurrent LAYOUTGET that would give us a usable lseg.

Lift the retry logic into pnfs_update_layout instead. That allows
us to redo the layout search, and may spare us from having to issue
an RPC.
Signed-off-by: NJeff Layton <jeff.layton@primarydata.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/pnfs.c

@@ -839,7 +839,6 @@ send_layoutget(struct pnfs_layout_hdr *lo,
 	struct inode *ino = lo->plh_inode;
 	struct nfs_server *server = NFS_SERVER(ino);
 	struct nfs4_layoutget *lgp;
-	struct pnfs_layout_segment *lseg;
 	loff_t i_size;
 
 	dprintk("--> %s\n", __func__);
@@ -849,10 +848,9 @@ send_layoutget(struct pnfs_layout_hdr *lo,
 	 * store in lseg. If we race with a concurrent seqid morphing
 	 * op, then re-send the LAYOUTGET.
 	 */
-	do {
 	lgp = kzalloc(sizeof(*lgp), gfp_flags);
 	if (lgp == NULL)
-			return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	i_size = i_size_read(ino);
 
@@ -873,21 +871,7 @@ send_layoutget(struct pnfs_layout_hdr *lo,
 	lgp->gfp_flags = gfp_flags;
 	lgp->cred = lo->plh_lc_cred;
 
-		lseg = nfs4_proc_layoutget(lgp, gfp_flags);
-	} while (lseg == ERR_PTR(-EAGAIN));
-
-	if (IS_ERR(lseg)) {
-		if (!nfs_error_is_fatal(PTR_ERR(lseg))) {
-			pnfs_layout_clear_fail_bit(lo,
-					pnfs_iomode_to_fail_bit(range->iomode));
-			lseg = NULL;
-		}
-	} else {
-		pnfs_layout_clear_fail_bit(lo,
-				pnfs_iomode_to_fail_bit(range->iomode));
-	}
-
-	return lseg;
+	return nfs4_proc_layoutget(lgp, gfp_flags);
 }
 
 static void pnfs_clear_layoutcommit(struct inode *inode,
@@ -1649,6 +1633,22 @@ pnfs_update_layout(struct inode *ino,
 		arg.length = PAGE_ALIGN(arg.length);
 
 	lseg = send_layoutget(lo, ctx, &arg, gfp_flags);
+	if (IS_ERR(lseg)) {
+		if (lseg == ERR_PTR(-EAGAIN)) {
+			if (first)
+				pnfs_clear_first_layoutget(lo);
+			pnfs_put_layout_hdr(lo);
+			goto lookup_again;
+		}
+
+		if (!nfs_error_is_fatal(PTR_ERR(lseg))) {
+			pnfs_layout_clear_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
+			lseg = NULL;
+		}
+	} else {
+		pnfs_layout_clear_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
+	}
+
 	atomic_dec(&lo->plh_outstanding);
 	trace_pnfs_update_layout(ino, pos, count, iomode, lo,
 				 PNFS_UPDATE_LAYOUT_SEND_LAYOUTGET);