Re: [PATCH v22 14/16] xfs: Add delattr mount option

Dave Chinner
2021-07-28T02:13:08Z

On Tue, Jul 27, 2021 at 05:47:57PM -0700, Darrick J. Wong wrote:
> On Mon, Jul 26, 2021 at 11:20:51PM -0700, Allison Henderson wrote:
> > This patch adds a mount option to enable delayed attributes. Eventually
> > this can be removed when delayed attrs becomes permanent.
> >
> > Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
> > ---
> > fs/xfs/libxfs/xfs_attr.h | 2 +-
> > fs/xfs/xfs_mount.h | 1 +
> > fs/xfs/xfs_super.c | 11 ++++++++++-
> > fs/xfs/xfs_xattr.c | 2 ++
> > 4 files changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> > index c0c92bd3..d4e7521 100644
> > --- a/fs/xfs/libxfs/xfs_attr.h
> > +++ b/fs/xfs/libxfs/xfs_attr.h
> > @@ -30,7 +30,7 @@ struct xfs_attr_list_context;
> >
> > static inline bool xfs_hasdelattr(struct xfs_mount *mp)
> > {
> > - return false;
> > + return mp->m_flags & XFS_MOUNT_DELATTR;
> > }
> >
> > /*
> > diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> > index 66a47f5..2945868 100644
> > --- a/fs/xfs/xfs_mount.h
> > +++ b/fs/xfs/xfs_mount.h
> > @@ -257,6 +257,7 @@ typedef struct xfs_mount {
> > #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)
> > +#define XFS_MOUNT_DELATTR (1ULL << 28) /* enable delayed attributes */
>
> So uh while we're renaming things away from "delattr", maybe this ...
>
> LOGGED ATTRIBUTE RE PLAY
>
> ... really should become the "larp" debug-only mount option.
>
> XFS_MOUNT_LARP
>
> Yeah. Do it!!!
>
> > /*
> > * 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 2c9e26a..39d6645 100644
> > --- a/fs/xfs/xfs_super.c
> > +++ b/fs/xfs/xfs_super.c
> > @@ -94,7 +94,7 @@ 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_dax_enum,
> > + Opt_discard, Opt_nodiscard, Opt_dax, Opt_dax_enum, Opt_delattr
> > };
> >
> > static const struct fs_parameter_spec xfs_fs_parameters[] = {
> > @@ -139,6 +139,7 @@ static const struct fs_parameter_spec xfs_fs_parameters[] = {
> > fsparam_flag("nodiscard", Opt_nodiscard),
> > fsparam_flag("dax", Opt_dax),
> > fsparam_enum("dax", Opt_dax_enum, dax_param_enums),
> > + fsparam_flag("delattr", Opt_delattr),
>
> I think you need this line to be guarded by #ifdefs so that the mount
> options parsing code will reject -o larp on non-debug kernels.

As i mentioned on #xfs, this really should be like the "always_cow"
debug option - access it via /sys/fs/xfs/debug/larping_with_larts -
rather than being a mount option that users might accidentally
discover and start using...

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com