xfs: deprecate barrier/nobarrier mount option

We always perform integrity operations now, so these mount options
don't do anything. Deprecate them and mark them for removal in
in a year.

Signed-Off-By: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

Documentation/filesystems/xfs.txt

@@ -51,13 +51,6 @@ default behaviour.
 	CRC enabled filesystems always use the attr2 format, and so
 	will reject the noattr2 mount option if it is set.
 
-  barrier (*)
-  nobarrier
-	Enables/disables the use of block layer write barriers for
-	writes into the journal and for data integrity operations.
-	This allows for drive level write caching to be enabled, for
-	devices that support write barriers.
-
   discard
   nodiscard (*)
 	Enable/disable the issuing of commands to let the block
@@ -228,7 +221,10 @@ default behaviour.
 Deprecated Mount Options
 ========================
 
-None at present.
+  Name				Removal Schedule
+  ----				----------------
+  barrier			no earlier than v4.15
+  nobarrier			no earlier than v4.15
 
 
 Removed Mount Options

fs/xfs/xfs_super.c

@@ -104,9 +104,6 @@ static const match_table_t tokens = {
 	{Opt_sysvgroups,"sysvgroups"},	/* group-ID from current process */
 	{Opt_allocsize,	"allocsize=%s"},/* preferred allocation size */
 	{Opt_norecovery,"norecovery"},	/* don't run XFS recovery */
-	{Opt_barrier,	"barrier"},	/* use writer barriers for log write and
-					 * unwritten extent conversion */
-	{Opt_nobarrier,	"nobarrier"},	/* .. disable */
 	{Opt_inode64,	"inode64"},	/* inodes can be allocated anywhere */
 	{Opt_inode32,   "inode32"},	/* inode allocation limited to
 					 * XFS_MAXINUMBER_32 */
@@ -134,6 +131,12 @@ static const match_table_t tokens = {
 	{Opt_nodiscard,	"nodiscard"},	/* Do not discard unused blocks */
 
 	{Opt_dax,	"dax"},		/* Enable direct access to bdev pages */
+
+	/* Deprecated mount options scheduled for removal */
+	{Opt_barrier,	"barrier"},	/* use writer barriers for log write and
+					 * unwritten extent conversion */
+	{Opt_nobarrier,	"nobarrier"},	/* .. disable */
+
 	{Opt_err,	NULL},
 };
 
@@ -301,12 +304,6 @@ xfs_parseargs(
 		case Opt_nouuid:
 			mp->m_flags |= XFS_MOUNT_NOUUID;
 			break;
-		case Opt_barrier:
-			mp->m_flags |= XFS_MOUNT_BARRIER;
-			break;
-		case Opt_nobarrier:
-			mp->m_flags &= ~XFS_MOUNT_BARRIER;
-			break;
 		case Opt_ikeep:
 			mp->m_flags |= XFS_MOUNT_IKEEP;
 			break;
@@ -374,6 +371,14 @@ xfs_parseargs(
 			mp->m_flags |= XFS_MOUNT_DAX;
 			break;
 #endif
+		case Opt_barrier:
+			xfs_warn(mp, "%s option is deprecated, ignoring.", p);
+			mp->m_flags |= XFS_MOUNT_BARRIER;
+			break;
+		case Opt_nobarrier:
+			xfs_warn(mp, "%s option is deprecated, ignoring.", p);
+			mp->m_flags &= ~XFS_MOUNT_BARRIER;
+			break;
 		default:
 			xfs_warn(mp, "unknown mount option [%s].", p);
 			return -EINVAL;
@@ -1238,9 +1243,11 @@ xfs_fs_remount(
 		token = match_token(p, tokens, args);
 		switch (token) {
 		case Opt_barrier:
+			xfs_warn(mp, "%s option is deprecated, ignoring.", p);
 			mp->m_flags |= XFS_MOUNT_BARRIER;
 			break;
 		case Opt_nobarrier:
+			xfs_warn(mp, "%s option is deprecated, ignoring.", p);
 			mp->m_flags &= ~XFS_MOUNT_BARRIER;
 			break;
 		case Opt_inode64: