From 02beb2686ff964884756c581d513e103542dcc6a Mon Sep 17 00:00:00 2001
From: Ira Weiny <ira.weiny@intel.com>
Date: Thu, 30 Apr 2020 07:41:35 -0700
Subject: [PATCH] fs/xfs: Make DAX mount option a tri-state
Git-commit: 02beb2686ff964884756c581d513e103542dcc6a
Patch-mainline: v5.8-rc1
References: jsc#SLE-13451

As agreed upon[1].  We make the dax mount option a tri-state.  '-o dax'
continues to operate the same.  We add 'always', 'never', and 'inode'
(default).

[1] https://lore.kernel.org/lkml/20200405061945.GA94792@iweiny-DESK2.sc.intel.com/

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Jan Kara <jack@suse.cz>

---
 fs/xfs/xfs_mount.h |    1 +
 fs/xfs/xfs_super.c |   47 +++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 44 insertions(+), 4 deletions(-)

--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -244,6 +244,7 @@ typedef struct xfs_mount {
 						   allocator */
 #define XFS_MOUNT_NOATTR2	(1ULL << 25)	/* disable use of attr2 format */
 #define XFS_MOUNT_DAX_ALWAYS	(1ULL << 26)
+#define XFS_MOUNT_DAX_NEVER	(1ULL << 27)
 
 
 /*
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -47,6 +47,32 @@ static struct kset *xfs_kset;		/* top-le
 static struct xfs_kobj xfs_dbg_kobj;	/* global debug sysfs attrs */
 #endif
 
+enum xfs_dax_mode {
+	XFS_DAX_INODE = 0,
+	XFS_DAX_ALWAYS = 1,
+	XFS_DAX_NEVER = 2,
+};
+
+static void
+xfs_mount_set_dax_mode(
+	struct xfs_mount	*mp,
+	enum xfs_dax_mode	mode)
+{
+	switch (mode) {
+	case XFS_DAX_INODE:
+		mp->m_flags &= ~(XFS_MOUNT_DAX_ALWAYS | XFS_MOUNT_DAX_NEVER);
+		break;
+	case XFS_DAX_ALWAYS:
+		mp->m_flags |= XFS_MOUNT_DAX_ALWAYS;
+		mp->m_flags &= ~XFS_MOUNT_DAX_NEVER;
+		break;
+	case XFS_DAX_NEVER:
+		mp->m_flags |= XFS_MOUNT_DAX_NEVER;
+		mp->m_flags &= ~XFS_MOUNT_DAX_ALWAYS;
+		break;
+	}
+}
+
 /*
  * Table driven mount option parser.
  */
@@ -59,7 +85,8 @@ enum {
 	Opt_filestreams, Opt_quota, Opt_noquota, Opt_usrquota, Opt_grpquota,
 	Opt_prjquota, Opt_uquota, Opt_gquota, Opt_pquota,
 	Opt_uqnoenforce, Opt_gqnoenforce, Opt_pqnoenforce, Opt_qnoenforce,
-	Opt_discard, Opt_nodiscard, Opt_dax, Opt_err,
+	Opt_discard, Opt_nodiscard, Opt_dax, Opt_dax_always, Opt_dax_never,
+	Opt_dax_inode, Opt_err,
 };
 
 static const match_table_t tokens = {
@@ -106,6 +133,10 @@ static const match_table_t tokens = {
 	{Opt_discard,	"discard"},	/* Discard unused blocks */
 	{Opt_nodiscard,	"nodiscard"},	/* Do not discard unused blocks */
 	{Opt_dax,	"dax"},		/* Enable direct access to bdev pages */
+	{Opt_dax_always, "dax=always"},	/* Enable direct access to bdev pages */
+	{Opt_dax_never,	"dax=never"},	/* Disable direct access to bdev pages */
+	{Opt_dax_inode,	"dax=inode"},	/* Enable direct access to bdev pages
+					 * for marked inodes */
 	{Opt_err,	NULL},
 };
 
@@ -335,7 +366,14 @@ xfs_parseargs(
 			break;
 #ifdef CONFIG_FS_DAX
 		case Opt_dax:
-			mp->m_flags |= XFS_MOUNT_DAX_ALWAYS;
+		case Opt_dax_always:
+			xfs_mount_set_dax_mode(mp, XFS_DAX_ALWAYS);
+			break;
+		case Opt_dax_never:
+			xfs_mount_set_dax_mode(mp, XFS_DAX_NEVER);
+			break;
+		case Opt_dax_inode:
+			xfs_mount_set_dax_mode(mp, XFS_DAX_INODE);
 			break;
 #endif
 		default:
@@ -449,7 +487,8 @@ xfs_showargs(
 		{ XFS_MOUNT_GRPID,		",grpid" },
 		{ XFS_MOUNT_DISCARD,		",discard" },
 		{ XFS_MOUNT_SMALL_INUMS,	",inode32" },
-		{ XFS_MOUNT_DAX_ALWAYS,		",dax" },
+		{ XFS_MOUNT_DAX_ALWAYS,		",dax=always" },
+		{ XFS_MOUNT_DAX_NEVER,		",dax=never" },
 		{ 0, NULL }
 	};
 	static struct proc_xfs_info xfs_info_unset[] = {
@@ -1686,7 +1725,7 @@ xfs_fs_fill_super(
 		if (!rtdev_is_dax && !datadev_is_dax) {
 			xfs_alert(mp,
 			"DAX unsupported by block device. Turning off DAX.");
-			mp->m_flags &= ~XFS_MOUNT_DAX_ALWAYS;
+			xfs_mount_set_dax_mode(mp, XFS_DAX_NEVER);
 		}
 		if (xfs_sb_version_hasreflink(&mp->m_sb)) {
 			xfs_alert(mp,