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

[Allison Henderson <allison.henderson@xxxxxxxxxx>]

On 7/27/21 7:13 PM, Dave Chinner wrote:
> 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@xxxxxxxxxx>
> > > ---
> > >   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.
Sure, if folks are ok with that, I'll take a look at always_cow, and see 
if I can put together something similar for larp.  Or larping_with_larts 
if folks prefer :-)  Thanks for the review!

Allison
>