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Subject[PATCH V6 4/8] fs/xfs: Make DAX mount option a tri-state
Date
From: Ira Weiny <ira.weiny@intel.com>

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 'iflag'
(default).

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

Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Changes from v5:
New Patch
---
fs/xfs/xfs_iops.c | 2 +-
fs/xfs/xfs_mount.h | 26 +++++++++++++++++++++++++-
fs/xfs/xfs_super.c | 34 +++++++++++++++++++++++++++++-----
3 files changed, 55 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 81f2f93caec0..1ec4a36917bd 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1248,7 +1248,7 @@ xfs_inode_supports_dax(
return false;

/* DAX mount option or DAX iflag must be set. */
- if (!(mp->m_flags & XFS_MOUNT_DAX) &&
+ if (xfs_mount_dax_mode(mp) != XFS_DAX_ALWAYS &&
!(ip->i_d.di_flags2 & XFS_DIFLAG2_DAX))
return false;

diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 88ab09ed29e7..ce027ee06692 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -233,7 +233,31 @@ typedef struct xfs_mount {
allocator */
#define XFS_MOUNT_NOATTR2 (1ULL << 25) /* disable use of attr2 format */

-#define XFS_MOUNT_DAX (1ULL << 62) /* TEST ONLY! */
+/* DAX flag is a 2 bit field representing a tri-state for dax
+ * iflag, always, never
+ * We reserve/document the 2 bits using dax field/field2
+ */
+#define XFS_DAX_FIELD_MASK 0x3ULL
+#define XFS_DAX_FIELD_SHIFT 62
+#define XFS_MOUNT_DAX_FIELD (1ULL << 62)
+#define XFS_MOUNT_DAX_FIELD2 (1ULL << 63)
+
+enum {
+ XFS_DAX_IFLAG = 0,
+ XFS_DAX_ALWAYS = 1,
+ XFS_DAX_NEVER = 2,
+};
+
+static inline void xfs_mount_set_dax(struct xfs_mount *mp, u32 val)
+{
+ mp->m_flags &= ~(XFS_DAX_FIELD_MASK << XFS_DAX_FIELD_SHIFT);
+ mp->m_flags |= ((val & XFS_DAX_FIELD_MASK) << XFS_DAX_FIELD_SHIFT);
+}
+
+static inline u32 xfs_mount_dax_mode(struct xfs_mount *mp)
+{
+ return (mp->m_flags >> XFS_DAX_FIELD_SHIFT) & XFS_DAX_FIELD_MASK;
+}

/*
* Max and min values for mount-option defined I/O
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 2094386af8ac..d2fd465eeed5 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -47,6 +47,13 @@ static struct kset *xfs_kset; /* top-level xfs sysfs dir */
static struct xfs_kobj xfs_dbg_kobj; /* global debug sysfs attrs */
#endif

+static const struct constant_table dax_param_enums[] = {
+ {"iflag", XFS_DAX_IFLAG },
+ {"always", XFS_DAX_ALWAYS },
+ {"never", XFS_DAX_NEVER },
+ {}
+};
+
/*
* Table driven mount option parser.
*/
@@ -59,7 +66,7 @@ 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_discard, Opt_nodiscard, Opt_dax, Opt_dax_enum,
};

static const struct fs_parameter_spec xfs_fs_parameters[] = {
@@ -103,6 +110,7 @@ static const struct fs_parameter_spec xfs_fs_parameters[] = {
fsparam_flag("discard", Opt_discard),
fsparam_flag("nodiscard", Opt_nodiscard),
fsparam_flag("dax", Opt_dax),
+ fsparam_enum("dax", Opt_dax_enum, dax_param_enums),
{}
};

@@ -129,7 +137,6 @@ xfs_fs_show_options(
{ XFS_MOUNT_GRPID, ",grpid" },
{ XFS_MOUNT_DISCARD, ",discard" },
{ XFS_MOUNT_LARGEIO, ",largeio" },
- { XFS_MOUNT_DAX, ",dax" },
{ 0, NULL }
};
struct xfs_mount *mp = XFS_M(root->d_sb);
@@ -185,6 +192,20 @@ xfs_fs_show_options(
if (!(mp->m_qflags & XFS_ALL_QUOTA_ACCT))
seq_puts(m, ",noquota");

+ switch (xfs_mount_dax_mode(mp)) {
+ case XFS_DAX_IFLAG:
+ seq_puts(m, ",dax=iflag");
+ break;
+ case XFS_DAX_ALWAYS:
+ seq_puts(m, ",dax=always");
+ break;
+ case XFS_DAX_NEVER:
+ seq_puts(m, ",dax=never");
+ break;
+ default:
+ break;
+ }
+
return 0;
}

@@ -1244,7 +1265,10 @@ xfs_fc_parse_param(
return 0;
#ifdef CONFIG_FS_DAX
case Opt_dax:
- mp->m_flags |= XFS_MOUNT_DAX;
+ xfs_mount_set_dax(mp, XFS_DAX_ALWAYS);
+ return 0;
+ case Opt_dax_enum:
+ xfs_mount_set_dax(mp, result.uint_32);
return 0;
#endif
default:
@@ -1437,7 +1461,7 @@ xfs_fc_fill_super(
if (XFS_SB_VERSION_NUM(&mp->m_sb) == XFS_SB_VERSION_5)
sb->s_flags |= SB_I_VERSION;

- if (mp->m_flags & XFS_MOUNT_DAX) {
+ if (xfs_mount_dax_mode(mp) == XFS_DAX_ALWAYS) {
bool rtdev_is_dax = false, datadev_is_dax;

xfs_warn(mp,
@@ -1451,7 +1475,7 @@ xfs_fc_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;
+ xfs_mount_set_dax(mp, XFS_DAX_NEVER);
}
if (xfs_sb_version_hasreflink(&mp->m_sb)) {
xfs_alert(mp,
--
2.25.1
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