pnfs: Add barrier to prevent lgopen using LAYOUTGET during recall

Since the LAYOUTGET on OPEN can be sent without prior inode information,
existing methods to prevent LAYOUTGET from being sent while processing
CB_LAYOUTRECALL don't work.  Track if a recall occurred while LAYOUTGET
was being sent, and if so ignore the results.
Signed-off-by: Fred Isaman <fred.isaman@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/callback_proc.c

@@ -322,6 +322,8 @@ static u32 initiate_bulk_draining(struct nfs_client *clp,
 static u32 do_callback_layoutrecall(struct nfs_client *clp,
 				    struct cb_layoutrecallargs *args)
 {
+	write_seqcount_begin(&clp->cl_callback_count);
+	write_seqcount_end(&clp->cl_callback_count);
 	if (args->cbl_recall_type == RETURN_FILE)
 		return initiate_file_draining(clp, args);
 	return initiate_bulk_draining(clp, args);

fs/nfs/pnfs.c

@@ -1017,6 +1017,7 @@ pnfs_alloc_init_layoutget_args(struct inode *ino,
 	nfs4_stateid_copy(&lgp->args.stateid, stateid);
 	lgp->gfp_flags = gfp_flags;
 	lgp->cred = get_rpccred(ctx->cred);
+	lgp->callback_count = raw_seqcount_begin(&server->nfs_client->cl_callback_count);
 	return lgp;
 }
 
@@ -2101,6 +2102,7 @@ void pnfs_parse_lgopen(struct inode *ino, struct nfs4_layoutget *lgp,
 {
 	struct pnfs_layout_hdr *lo;
 	struct pnfs_layout_segment *lseg;
+	struct nfs_server *srv = NFS_SERVER(ino);
 	u32 iomode;
 
 	if (!lgp)
@@ -2116,7 +2118,7 @@ void pnfs_parse_lgopen(struct inode *ino, struct nfs4_layoutget *lgp,
 			/* FIXME - Any error not listed above permanently
 			 * halts lgopen attempts.
 			 */
-			NFS_SERVER(ino)->caps &= ~NFS_CAP_LGOPEN;
+			srv->caps &= ~NFS_CAP_LGOPEN;
 		}
 		return;
 	}
@@ -2129,6 +2131,9 @@ void pnfs_parse_lgopen(struct inode *ino, struct nfs4_layoutget *lgp,
 		lo = NFS_I(lgp->args.inode)->layout;
 	pnfs_get_layout_hdr(lo);
 
+	if (read_seqcount_retry(&srv->nfs_client->cl_callback_count,
+				lgp->callback_count))
+		goto out;
 	lseg = pnfs_layout_process(lgp);
 	atomic_dec(&lo->plh_outstanding);
 	if (IS_ERR(lseg)) {
@@ -2139,6 +2144,7 @@ void pnfs_parse_lgopen(struct inode *ino, struct nfs4_layoutget *lgp,
 		pnfs_layout_clear_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
 		pnfs_put_lseg(lseg);
 	}
+out:
 	pnfs_clear_first_layoutget(lo);
 	pnfs_put_layout_hdr(lo);
 }

include/linux/nfs_fs_sb.h

@@ -28,6 +28,7 @@ struct nfs41_impl_id;
 struct nfs_client {
 	refcount_t		cl_count;
 	atomic_t		cl_mds_count;
+	seqcount_t		cl_callback_count;
 	int			cl_cons_state;	/* current construction state (-ve: init error) */
 #define NFS_CS_READY		0		/* ready to be used */
 #define NFS_CS_INITING		1		/* busy initialising */

include/linux/nfs_xdr.h

@@ -271,6 +271,7 @@ struct nfs4_layoutget {
 	struct nfs4_layoutget_args args;
 	struct nfs4_layoutget_res res;
 	struct rpc_cred *cred;
+	unsigned callback_count;
 	gfp_t gfp_flags;
 };