From c770f997a4227b6fc5f62275b2337622213e35af Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Wed, 11 Mar 2026 12:25:00 -0400 Subject: [PATCH] xfs: only flush when COW fork blocks overlap data fork holes The zero range hole mapping flush case has been lifted from iomap into XFS. Now that we have more mapping context available from the ->iomap_begin() handler, we can isolate the flush further to when we know a hole is fronted by COW blocks. Rather than purely rely on pagecache dirty state, explicitly check for the case where a range is a hole in both forks. Otherwise trim to the range where there does happen to be overlap and use that for the pagecache writeback check. This might prevent some spurious zeroing, but more importantly makes it easier to remove the flush entirely. Signed-off-by: Brian Foster Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Carlos Maiolino --- fs/xfs/xfs_iomap.c | 36 ++++++++++++++++++++++++++++++------ 1 file changed, 30 insertions(+), 6 deletions(-) diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index df1eab646cae..6229a0bf793b 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -1781,10 +1781,12 @@ xfs_buffered_write_iomap_begin( { struct iomap_iter *iter = container_of(iomap, struct iomap_iter, iomap); + struct address_space *mapping = inode->i_mapping; struct xfs_inode *ip = XFS_I(inode); struct xfs_mount *mp = ip->i_mount; xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset); xfs_fileoff_t end_fsb = xfs_iomap_end_fsb(mp, offset, count); + xfs_fileoff_t cow_fsb = NULLFILEOFF; struct xfs_bmbt_irec imap, cmap; struct xfs_iext_cursor icur, ccur; xfs_fsblock_t prealloc_blocks = 0; @@ -1852,6 +1854,8 @@ restart: } cow_eof = !xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &ccur, &cmap); + if (!cow_eof) + cow_fsb = cmap.br_startoff; } /* We never need to allocate blocks for unsharing a hole. */ @@ -1866,17 +1870,37 @@ restart: * writeback to remap pending blocks and restart the lookup. */ if ((flags & IOMAP_ZERO) && imap.br_startoff > offset_fsb) { - if (filemap_range_needs_writeback(inode->i_mapping, offset, - offset + count - 1)) { + loff_t start, end; + + imap.br_blockcount = imap.br_startoff - offset_fsb; + imap.br_startoff = offset_fsb; + imap.br_startblock = HOLESTARTBLOCK; + imap.br_state = XFS_EXT_NORM; + + if (cow_fsb == NULLFILEOFF) + goto found_imap; + if (cow_fsb > offset_fsb) { + xfs_trim_extent(&imap, offset_fsb, + cow_fsb - offset_fsb); + goto found_imap; + } + + /* COW fork blocks overlap the hole */ + xfs_trim_extent(&imap, offset_fsb, + cmap.br_startoff + cmap.br_blockcount - offset_fsb); + start = XFS_FSB_TO_B(mp, imap.br_startoff); + end = XFS_FSB_TO_B(mp, + imap.br_startoff + imap.br_blockcount) - 1; + if (filemap_range_needs_writeback(mapping, start, end)) { xfs_iunlock(ip, lockmode); - error = filemap_write_and_wait_range(inode->i_mapping, - offset, offset + count - 1); + error = filemap_write_and_wait_range(mapping, start, + end); if (error) return error; goto restart; } - xfs_hole_to_iomap(ip, iomap, offset_fsb, imap.br_startoff); - goto out_unlock; + + goto found_imap; } /*