On Mon, Apr 21, 2025 at 06:47:44AM +0100, John Garry wrote:
> On 21/04/2025 05:00, Darrick J. Wong wrote:
> > > @@ -843,6 +909,8 @@ xfs_file_dio_write(
> > > return xfs_file_dio_write_unaligned(ip, iocb, from);
> > > if (xfs_is_zoned_inode(ip))
> > > return xfs_file_dio_write_zoned(ip, iocb, from);
> > What happens to an IOCB_ATOMIC write to a zoned file? I think the
> > ioend for an atomic write to a zoned file involves a similar change as
> > an outofplace atomic write to a file (one big transaction to absorb
> > all the mapping changes) but I don't think the zoned code quite does
> > that...?
>
> Correct. For now, I don't think that we should try to support zoned device
> atomic writes. However we don't have proper checks for this. How about
> adding a xfs_has_zoned() check in xfs_get_atomic_write_{min, max, opt}()?
Well it turns out that was a stupid question -- zoned=1 can't be enabled
with reflink, which means there's no cow fallback so atomic writes just
plain don't work:
$ xfs_info /mnt
meta-data=/dev/sda isize=512 agcount=4, agsize=32768 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=1
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
= exchange=1 metadir=1
data = bsize=4096 blocks=131072, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1, parent=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =internal extsz=4096 blocks=5061632, rtextents=5061632
= rgcount=78 rgsize=65536 extents
= zoned=1 start=131072 reserved=0
$ xfs_io -c 'statx -r -m 0x10000' /mnt/a | grep atomic
stat.atomic_write_unit_min = 0
stat.atomic_write_unit_max = 0
stat.atomic_write_segments_max = 0
stat.atomic_write_unit_max_opt = 0
I /think/ all you'd have to do is create an xfs_zoned_end_atomic_io
function that does what xfs_zoned_end_io but with a single
tr_atomic_ioend transaction; figure out how to convey "this is an
atomic out of place write" to xfs_end_ioend so that it knows to call
xfs_zoned_end_atomic_io; and then update the xfs_get_atomic_write*
helpers.
--D
> Thanks,
> John
