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SubjectRe: [PATCH] fs/stat: set attributes_mask for STATX_ATTR_DAX
Hi,

Thanks for review.

----- Original Message -----
> From: "Darrick J. Wong" <darrick.wong@oracle.com>
> To: "XiaoLi Feng" <xifeng@redhat.com>
> Cc: "Randy Dunlap" <rdunlap@infradead.org>, linux-kernel@vger.kernel.org, "ira weiny" <ira.weiny@intel.com>, "Xiaoli
> Feng" <fengxiaoli0714@gmail.com>, "linux-fsdevel" <linux-fsdevel@vger.kernel.org>
> Sent: Saturday, November 21, 2020 10:03:18 AM
> Subject: Re: [PATCH] fs/stat: set attributes_mask for STATX_ATTR_DAX
>
> [Adding fsdevel to cc since this is a filesystems question]
>
> On Fri, Nov 20, 2020 at 04:58:09PM -0800, Randy Dunlap wrote:
> > Hi,
> >
> > I don't know this code, but:
> >
> > On 11/20/20 4:33 PM, XiaoLi Feng wrote:
> > > From: Xiaoli Feng <fengxiaoli0714@gmail.com>
> > >
> > > keep attributes and attributes_mask are consistent for
> > > STATX_ATTR_DAX.
> > > ---
> > > fs/stat.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/fs/stat.c b/fs/stat.c
> > > index dacecdda2e79..914a61d256b0 100644
> > > --- a/fs/stat.c
> > > +++ b/fs/stat.c
> > > @@ -82,7 +82,7 @@ int vfs_getattr_nosec(const struct path *path, struct
> > > kstat *stat,
> > >
> > > if (IS_DAX(inode))
> > > stat->attributes |= STATX_ATTR_DAX;
> > > -
> > > + stat->attributes_mask |= STATX_ATTR_DAX;
> >
> > Why shouldn't that be:
> >
> > if (IS_DAX(inode))
> > stat->attributes_mask |= STATX_ATTR_DAX;
> >
> > or combine them, like this:
> >
> > if (IS_DAX(inode)) {
> > stat->attributes |= STATX_ATTR_DAX;
> > stat->attributes_mask |= STATX_ATTR_DAX;
> > }
> >
> >
> > and no need to delete that blank line.
>
> Some filesystems could support DAX but not have it enabled for this
> particular file, so this won't work.
>
> General question: should filesystems that are /capable/ of DAX signal
> this by setting the DAX bit in the attributes mask? Or is this a VFS
> feature and hence here is the appropriate place to be setting the mask?

Actually I just see here set the attributes. Then set the attributes mask
after it.

>
> Extra question: should we only set this in the attributes mask if
> CONFIG_FS_DAX=y ?

No, my origin patch always set this attributes mask. It's out of if condition.

if (IS_DAX(inode))
stat->attributes |= STATX_ATTR_DAX;
-
+ stat->attributes_mask |= STATX_ATTR_DAX;

>
> --D
>
> > > if (inode->i_op->getattr)
> > > return inode->i_op->getattr(path, stat, request_mask,
> > > query_flags);
> > >
> >
> > thanks.
> > --
> > ~Randy
> >
>
>

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