On Mon, Feb 05, 2024 at 01:10:54PM +0000, John Garry wrote:
> On 02/02/2024 18:05, Darrick J. Wong wrote:
> > On Wed, Jan 24, 2024 at 02:26:43PM +0000, John Garry wrote:
> > > Support providing info on atomic write unit min and max for an inode.
> > >
> > > For simplicity, currently we limit the min at the FS block size, but a
> > > lower limit could be supported in future.
> > >
> > > The atomic write unit min and max is limited by the guaranteed extent
> > > alignment for the inode.
> > >
> > > Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
> > > ---
> > > fs/xfs/xfs_iops.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
> > > fs/xfs/xfs_iops.h | 4 ++++
> > > 2 files changed, 49 insertions(+)
> > >
> > > diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> > > index a0d77f5f512e..0890d2f70f4d 100644
> > > --- a/fs/xfs/xfs_iops.c
> > > +++ b/fs/xfs/xfs_iops.c
> > > @@ -546,6 +546,44 @@ xfs_stat_blksize(
> > > return PAGE_SIZE;
> > > }
> > > +void xfs_get_atomic_write_attr(
> >
> > static void?
>
> We use this in the iomap and statx code
>
> >
> > > + struct xfs_inode *ip,
> > > + unsigned int *unit_min,
> > > + unsigned int *unit_max)
> >
> > Weird indenting here.
>
> hmmm... I thought that this was the XFS style
>
> Can you show how it should look?
The parameter declarations should line up with the local variables:
void
xfs_get_atomic_write_attr(
struct xfs_inode *ip,
unsigned int *unit_min,
unsigned int *unit_max)
{
struct xfs_buftarg *target = xfs_inode_buftarg(ip);
struct block_device *bdev = target->bt_bdev;
struct request_queue *q = bdev->bd_queue;
struct xfs_mount *mp = ip->i_mount;
unsigned int awu_min, awu_max, align;
xfs_extlen_t extsz = xfs_get_extsz(ip);
> >
> > > +{
> > > + xfs_extlen_t extsz = xfs_get_extsz(ip);
> > > + struct xfs_buftarg *target = xfs_inode_buftarg(ip);
> > > + struct block_device *bdev = target->bt_bdev;
> > > + unsigned int awu_min, awu_max, align;
> > > + struct request_queue *q = bdev->bd_queue;
> > > + struct xfs_mount *mp = ip->i_mount;
> > > +
> > > + /*
> > > + * Convert to multiples of the BLOCKSIZE (as we support a minimum
> > > + * atomic write unit of BLOCKSIZE).
> > > + */
> > > + awu_min = queue_atomic_write_unit_min_bytes(q);
> > > + awu_max = queue_atomic_write_unit_max_bytes(q);
> > > +
> > > + awu_min &= ~mp->m_blockmask;
> >
> > Why do you round /down/ the awu_min value here?
>
> This is just to ensure that we returning *unit_min >= BLOCKSIZE
>
> For example, if awu_min, max 1K, 64K from the bdev, we now have 0 and 64K.
> And below this gives us awu_min, max of 4k, 64k.
>
> Maybe there is a more logical way of doing this.
awu_min = roundup(queue_atomic_write_unit_min_bytes(q),
mp->m_sb.sb_blocksize);
?
>
> >
> > > + awu_max &= ~mp->m_blockmask;
> >
> > Actually -- since the atomic write units have to be powers of 2, why is
> > rounding needed here at all?
>
> Sure, but the bdev can report a awu_min < BLOCKSIZE
>
> >
> > > +
> > > + align = XFS_FSB_TO_B(mp, extsz);
> > > +
> > > + if (!awu_max || !xfs_inode_atomicwrites(ip) || !align ||
> > > + !is_power_of_2(align)) {
> >
> > ...and if you take my suggestion to make a common helper to validate the
> > atomic write unit parameters, this can collapse into:
> >
> > alloc_unit_bytes = xfs_inode_alloc_unitsize(ip);
> > if (!xfs_inode_has_atomicwrites(ip) ||
> > !bdev_validate_atomic_write(bdev, alloc_unit_bytes)) > /* not supported, return zeroes */
> > *unit_min = 0;
> > *unit_max = 0;
> > return;
> > }
> >
> > *unit_min = max(alloc_unit_bytes, awu_min);
> > *unit_max = min(alloc_unit_bytes, awu_max);
>
> Again, we need to ensure that *unit_min >= BLOCKSIZE
The file allocation unit and hence the return value of
xfs_inode_alloc_unitsize is always a multiple of sb_blocksize.
--D
> Thanks,
> John
>
>
