On Wed, Nov 21, 2018 at 10:09:36AM -0800, Darrick J. Wong wrote: > On Tue, Nov 20, 2018 at 08:04:58AM +1100, Dave Chinner wrote: > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > > > Just tried to punch a 40T sparse file when enospc was triggered due > > to extent size hints consuming more space than expected. It failed > > with: > > > > # sudo xfs_io -c "fpunch 0 40t" /mnt/fast/xfs-arekm.img > > fallocate: No space left on device > > # > > > > because the writeback error of ENOSPC was being reported. We're > > going to free that space, so we don't care if there was a ENOSPC > > writeback error. So ignore ENOSPC errors and punch anyway. > > > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> > > --- > > fs/xfs/xfs_bmap_util.c | 7 ++++++- > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c > > index 167ff4297e5c..cc7a0d47c529 100644 > > --- a/fs/xfs/xfs_bmap_util.c > > +++ b/fs/xfs/xfs_bmap_util.c > > @@ -1060,8 +1060,13 @@ xfs_flush_unmap_range( > > start = round_down(offset, rounding); > > end = round_up(offset + len, rounding) - 1; > > > > + /* > > + * We're going to trash the data in this range, so if writeback reports > > + * an enospc error, don't let it stop us from /freeing the space/ in the > > + * range to alleviate the ENOSPC condition. > > + */ > > error = filemap_write_and_wait_range(inode->i_mapping, start, end); > > - if (error) > > + if (error && error != -ENOSPC) > > I think there's a bug here -- COLLAPSE_RANGE and INSERT_RANGE call > xfs_prepare_shift to writeback and invalidate the pagecache from a > selected offset to EOF, and _prepare_shift calls _flush_unmap_range. > > So if we have a dirty 100 block file and we ask xfs to collapse 3 blocks > at block 17, it'll _prepare_shift blocks 20-99 before shifting them down > by 3 blocks. If we instead asked to insert 3 blocks at block 17, it'll > _prepare_shift blocks 17-99 before shifting them up by 3 blocks. > > Unlike the punch/reflink cases, the _prepare_shift ranges aren't doomed, > so the user might want to know if the write fails. Hmmm, yeah, the _prepare_shift changes came after this patch, so I didn't consider that when originally writing this patch. Drop it for now, will have to rethink what to do here.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
