NFSv4: Detect support for OPEN4_SHARE_ACCESS_WANT_OPEN_XOR_DELEGATION

If the server supports the NFSv4.2 protocol extension to optimise away
returning a stateid when it returns a delegation, then we cache that
information in another capability flag.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Lance Shelton <lance.shelton@hammerspace.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfs4proc.c

@@ -3990,6 +3990,10 @@ static int _nfs4_server_capabilities(struct nfs_server *server, struct nfs_fh *f
 				sizeof(server->attr_bitmask));
 		server->attr_bitmask_nl[2] &= ~FATTR4_WORD2_SECURITY_LABEL;
 
+		if (res.open_caps.oa_share_access_want[0] &
+		    NFS4_SHARE_WANT_OPEN_XOR_DELEGATION)
+			server->caps |= NFS_CAP_OPEN_XOR;
+
 		memcpy(server->cache_consistency_bitmask, res.attr_bitmask, sizeof(server->cache_consistency_bitmask));
 		server->cache_consistency_bitmask[0] &= FATTR4_WORD0_CHANGE|FATTR4_WORD0_SIZE;
 		server->cache_consistency_bitmask[1] &= FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY;

include/linux/nfs_fs_sb.h

@@ -278,6 +278,7 @@ struct nfs_server {
 #define NFS_CAP_LGOPEN		(1U << 5)
 #define NFS_CAP_CASE_INSENSITIVE	(1U << 6)
 #define NFS_CAP_CASE_PRESERVING	(1U << 7)
+#define NFS_CAP_OPEN_XOR	(1U << 12)
 #define NFS_CAP_DELEGTIME	(1U << 13)
 #define NFS_CAP_POSIX_LOCK	(1U << 14)
 #define NFS_CAP_UIDGID_NOMAP	(1U << 15)

include/uapi/linux/nfs4.h

@@ -46,6 +46,7 @@
 #define NFS4_OPEN_RESULT_CONFIRM		0x0002
 #define NFS4_OPEN_RESULT_LOCKTYPE_POSIX		0x0004
 #define NFS4_OPEN_RESULT_PRESERVE_UNLINKED	0x0008
+#define NFS4_OPEN_RESULT_NO_OPEN_STATEID	0x0010
 #define NFS4_OPEN_RESULT_MAY_NOTIFY_LOCK	0x0020
 
 #define NFS4_SHARE_ACCESS_MASK	0x000F
@@ -70,6 +71,7 @@
 #define NFS4_SHARE_PUSH_DELEG_WHEN_UNCONTENDED		0x20000
 
 #define NFS4_SHARE_WANT_DELEG_TIMESTAMPS		0x100000
+#define NFS4_SHARE_WANT_OPEN_XOR_DELEGATION		0x200000
 
 #define NFS4_CDFC4_FORE	0x1
 #define NFS4_CDFC4_BACK 0x2