On Wed, May 01, 2024 at 10:53:28AM +1000, Dave Chinner wrote:
> On Mon, Apr 29, 2024 at 05:47:37PM +0000, John Garry wrote:
> > Like we already do for rtvol, only free full extents for forcealign in
> > xfs_free_file_space().
> >
> > Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
> > ---
> > fs/xfs/xfs_bmap_util.c | 7 +++++--
> > 1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> > index f26d1570b9bd..1dd45dfb2811 100644
> > --- a/fs/xfs/xfs_bmap_util.c
> > +++ b/fs/xfs/xfs_bmap_util.c
> > @@ -847,8 +847,11 @@ xfs_free_file_space(
> > startoffset_fsb = XFS_B_TO_FSB(mp, offset);
> > endoffset_fsb = XFS_B_TO_FSBT(mp, offset + len);
> >
> > - /* We can only free complete realtime extents. */
> > - if (XFS_IS_REALTIME_INODE(ip) && mp->m_sb.sb_rextsize > 1) {
> > + /* Free only complete extents. */
> > + if (xfs_inode_has_forcealign(ip) && ip->i_extsize > 1) {
> > + startoffset_fsb = roundup_64(startoffset_fsb, ip->i_extsize);
> > + endoffset_fsb = rounddown_64(endoffset_fsb, ip->i_extsize);
> > + } else if (XFS_IS_REALTIME_INODE(ip) && mp->m_sb.sb_rextsize > 1) {
> > startoffset_fsb = xfs_rtb_roundup_rtx(mp, startoffset_fsb);
> > endoffset_fsb = xfs_rtb_rounddown_rtx(mp, endoffset_fsb);
> > }
>
> When you look at xfs_rtb_roundup_rtx() you'll find it's just a one
> line wrapper around roundup_64().
I added this a couple of cycles ago to get ready for realtime
modernization. That will create a bunch *more* churn in my tree just to
convert everything *back*.
Where the hell were you when that was being reviewed?!!!
NO! This is pointless busywork!
--D
> So lets get rid of the obfuscation that the one line RT wrapper
> introduces, and it turns into this:
>
> rounding = 1;
> if (xfs_inode_has_forcealign(ip)
> rounding = ip->i_extsize;
> else if (XFS_IS_REALTIME_INODE(ip))
> rounding = mp->m_sb.sb_rextsize;
>
> if (rounding > 1) {
> startoffset_fsb = roundup_64(startoffset_fsb, rounding);
> endoffset_fsb = rounddown_64(endoffset_fsb, rounding);
> }
>
> What this points out is that the prep steps for fallocate operations
> also need to handle both forced alignment and rtextsize rounding,
> and it does neither right now. xfs_flush_unmap_range() is the main
> offender here, but xfs_prepare_shift() also needs fixing.
>
> Hence:
>
> static inline xfs_extlen_t
> xfs_extent_alignment(
> struct xfs_inode *ip)
> {
> if (xfs_inode_has_forcealign(ip))
> return ip->i_extsize;
> if (XFS_IS_REALTIME_INODE(ip))
> return mp->m_sb.sb_rextsize;
> return 1;
> }
>
>
> In xfs_flush_unmap_range():
>
> /*
> * Make sure we extend the flush out to extent alignment
> * boundaries so any extent range overlapping the start/end
> * of the modification we are about to do is clean and idle.
> */
> rounding = XFS_FSB_TO_B(mp, xfs_extent_alignment(ip));
> rounding = max(rounding, PAGE_SIZE);
> ...
>
> in xfs_free_file_space()
>
> /*
> * Round the range we are going to free inwards to extent
> * alignment boundaries so we don't free blocks outside the
> * range requested.
> */
> rounding = xfs_extent_alignment(ip);
> if (rounding > 1 ) {
> startoffset_fsb = roundup_64(startoffset_fsb, rounding);
> endoffset_fsb = rounddown_64(endoffset_fsb, rounding);
> }
>
> and in xfs_prepare_shift()
>
> /*
> * Shift operations must stabilize the start block offset boundary along
> * with the full range of the operation. If we don't, a COW writeback
> * completion could race with an insert, front merge with the start
> * extent (after split) during the shift and corrupt the file. Start
> * with the aligned block just prior to the start to stabilize the boundary.
> */
> rounding = XFS_FSB_TO_B(mp, xfs_extent_alignment(ip));
> offset = round_down(offset, rounding);
> if (offset)
> offset -= rounding;
>
> Also, I think that the changes I suggested earlier to
> xfs_is_falloc_aligned() could use this xfs_extent_alignment()
> helper...
>
> Overall this makes the code a whole lot easier to read and it also
> allows forced alignment to work correctly on RT devices...
>
> -Dave.
> --
> Dave Chinner
> david@xxxxxxxxxxxxx
>
