On Tue, Apr 02, 2019 at 10:56:32AM -0700, Darrick J. Wong wrote:
> On Tue, Apr 02, 2019 at 10:44:38AM -0500, Eric Sandeen wrote:
> > pmem is byte addressable, and indeed byte-aligned DIO works on
> > a DAX file. So, teach XFS_IOC_DIOINFO to return the correct
> > alignment information if IS_DAX(inode).
>
> If it's a DAX filesystem, do we want to try to steer people towards
> things like 2MB pages since (in theory) we can get away with fewer page
> table mappings? And (seeing as that's mmap that cares, not directio)
> would advertising preferential page mapping sizes be more appropriate
> advertised in a different ioctl?
>
> --D
>
> > Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> > ---
> >
> > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > index 6ecdbb3..35eae7d 100644
> > --- a/fs/xfs/xfs_ioctl.c
> > +++ b/fs/xfs/xfs_ioctl.c
> > @@ -1919,12 +1919,21 @@ xfs_file_ioctl(
> > }
> > case XFS_IOC_DIOINFO: {
> > struct dioattr da;
> > - xfs_buftarg_t *target =
> > - XFS_IS_REALTIME_INODE(ip) ?
> > - mp->m_rtdev_targp : mp->m_ddev_targp;
> >
> > - da.d_mem = da.d_miniosz = target->bt_logical_sectorsize;
> > - da.d_maxiosz = INT_MAX & ~(da.d_miniosz - 1);
> > + if (IS_DAX(inode)) {
> > + /* pmem is byte addressable */
> > + da.d_mem = 1;
> > + da.d_miniosz = 1;
> > + da.d_maxiosz = INT_MAX;
I don't think we want to open that can of worms.
Have you run fsx on dax mixing mmap/dio with byte range granularity?
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
