fs: Add new VFCF_xxx flags for va_filerev

Richard Kojedzinszky <[email protected]> reported a problem via
email, where the Linux NFSv4.2 client did not detect a change in a
directory on a FreeBSD NFSv4.2 server.

Adding support for the NFSv4.2 change_attr_type attribute seems
to have fixed the problem. This requires that the server file system
indicate if it increments va_filerev by one, since that file attribute
is used for the NFSv4.2 change attribute.  Fuse requires an indication
that va_filerev is based on ctime.

This patch adds VFCF_FILEREVINC and VFCF_FILEREVCT to indicate this.

A future patch to the NFS server will use these flags.

Reviewed by:	asomers, kib
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D48436

sys/sys/mount.h

@@ -685,6 +685,8 @@ struct ovfsconf {
 #define	VFCF_SBDRY	0x01000000	/* Stop at Boundary: defer stop requests
 					   to kernel->user (AST) transition */
 #define	VFCF_FILEMOUNT	0x02000000	/* allow mounting files */
+#define	VFCF_FILEREVINC	0x04000000	/* va_filerev is incr. by one */
+#define	VFCF_FILEREVCT	0x08000000	/* va_filerev is set to ctime */
 
 typedef uint32_t fsctlop_t;
 

sys/ufs/ffs/ffs_vfsops.c

@@ -117,7 +117,7 @@ static struct vfsops ufs_vfsops = {
 	.vfs_susp_clean =	process_deferred_inactive,
 };
 
-VFS_SET(ufs_vfsops, ufs, 0);
+VFS_SET(ufs_vfsops, ufs, VFCF_FILEREVINC);
 MODULE_VERSION(ufs, 1);
 
 static b_strategy_t ffs_geom_strategy;