[PATCH v3 4/7] xfs: always trim mapping to requested range for zero range

[Brian Foster <bfoster@redhat.com>]

Refactor and tweak the IOMAP_ZERO logic in preparation to support
filling the folio batch for unwritten mappings. Drop the superfluous
imap offset check since the hole case has already been filtered out.
Split the the delalloc case handling into a sub-branch, and always
trim the imap to the requested offset/count so it can be more easily
used to bound the range to lookup in pagecache.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/xfs/xfs_iomap.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index ff05e6b1b0bb..b5cf5bc6308d 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1756,21 +1756,20 @@ xfs_buffered_write_iomap_begin(
 	}
 
 	/*
-	 * For zeroing, trim a delalloc extent that extends beyond the EOF
-	 * block.  If it starts beyond the EOF block, convert it to an
+	 * For zeroing, trim extents that extend beyond the EOF block. If a
+	 * delalloc extent starts beyond the EOF block, convert it to an
 	 * unwritten extent.
 	 */
-	if ((flags & IOMAP_ZERO) && imap.br_startoff <= offset_fsb &&
-	    isnullstartblock(imap.br_startblock)) {
+	if (flags & IOMAP_ZERO) {
 		xfs_fileoff_t eof_fsb = XFS_B_TO_FSB(mp, XFS_ISIZE(ip));
 
-		if (offset_fsb >= eof_fsb)
+		if (isnullstartblock(imap.br_startblock) &&
+		    offset_fsb >= eof_fsb)
 			goto convert_delay;
-		if (end_fsb > eof_fsb) {
+		if (offset_fsb < eof_fsb && end_fsb > eof_fsb)
 			end_fsb = eof_fsb;
-			xfs_trim_extent(&imap, offset_fsb,
-					end_fsb - offset_fsb);
-		}
+
+		xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);
 	}
 
 	/*
-- 
2.50.0