Re: [PATCH V6 4/8] fs/xfs: Make DAX mount option a tri-state

Ira Weiny
2020-04-08T00:09:07Z

On Wed, Apr 08, 2020 at 09:59:09AM +1000, Dave Chinner wrote:
> On Tue, Apr 07, 2020 at 11:29:54AM -0700, ira.weiny@intel.com wrote:
> > 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;
> > +}
>
> This is overly complex. Just use 2 flags:

LOL... I was afraid someone would say that. At first I used 2 flags with
fsparam_string, but then I realized Darrick suggested fsparam_enum:

"It would be handy if we could have a single fsparam_enum for figuring
out the dax mount options."

-- https://lore.kernel.org/lkml/20200403183746.GQ80283@magnolia/

So I changed it...

Darrick?

Ira

>
> #define XFS_MOUNT_DAX_ALWAYS (1ULL << 26)
> #define XFS_MOUNT_DAX_NEVER (1ULL << 27)
>
> and if no mount flag is set, we use the inode flag....
>
> > @@ -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" },
> + { XFS_MOUNT_DAX_ALWAYS, ",dax=always" },
> + { XFS_MOUNT_DAX_NEVER, ",dax=never" },
>
> > { 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;
> > + }
>
> if (!(mp->m_flags & (XFS_MOUNT_DAX_ALWAYS | XFS_MOUNT_DAX_NEVER))
> seq_puts(m, ",dax=iflag");
>
> > +
> > 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) {
>
> if (mp->m_flags & XFS_MOUNT_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
> >
> >
>
> --
> Dave Chinner
> david@fromorbit.com