On Sat, Aug 10, 2024 at 08:18:16PM +0530, Souptick Joarder wrote:
> On Tue, Aug 6, 2024 at 12:16 AM Darrick J. Wong <djwong@xxxxxxxxxx> wrote:
> >
> > From: Darrick J. Wong <djwong@xxxxxxxxxx>
> >
> > If a file has the S_DAX flag (aka fsdax access mode) set, we cannot
> > allow users to change the realtime flag unless the datadev and rtdev
> > both support fsdax access modes. Even if there are no extents allocated
> > to the file, the setattr thread could be racing with another thread
> > that has already started down the write code paths.
> >
> > Fixes: ba23cba9b3bdc ("fs: allow per-device dax status checking for filesystems")
> > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> > ---
> > fs/xfs/xfs_ioctl.c | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > index 4e933db75b12..6b13666d4e96 100644
> > --- a/fs/xfs/xfs_ioctl.c
> > +++ b/fs/xfs/xfs_ioctl.c
> > @@ -483,6 +483,17 @@ xfs_ioctl_setattr_xflags(
> > /* Can't change realtime flag if any extents are allocated. */
> > if (ip->i_df.if_nextents || ip->i_delayed_blks)
> > return -EINVAL;
> > +
> > + /*
> > + * If S_DAX is enabled on this file, we can only switch the
> > + * device if both support fsdax. We can't update S_DAX because
> > + * there might be other threads walking down the access paths.
> > + */
> > + if (IS_DAX(VFS_I(ip)) &&
> > + (mp->m_ddev_targp->bt_daxdev == NULL ||
> > + (mp->m_rtdev_targp &&
> > + mp->m_rtdev_targp->bt_daxdev == NULL)))
> > + return -EINVAL;
> Any chance of mp->m_ddev_targp == NULL ?
No, m_ddev_targp is the device you give to mount. e.g. if you do
# mount /dev/sda /mnt
then m_ddev_targp is the block_device /dev/sda.
--D
> > }
> >
> > if (rtflag) {
> >
