[PATCH RFC 3/4] 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>
---
 fs/xfs/xfs_iomap.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 86da16f54be9..ed42a28973bb 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1029,17 +1029,16 @@ xfs_buffered_write_iomap_begin(
 	 * block.  If it starts beyond the EOF block, convert it to an
 	 * unwritten extent.
 	 */
-	if ((flags & IOMAP_ZERO) && imap.br_startoff <= offset_fsb &&
-	    isnullstartblock(imap.br_startblock)) {
-		xfs_fileoff_t eof_fsb = XFS_B_TO_FSB(mp, XFS_ISIZE(ip));
-
-		if (offset_fsb >= eof_fsb)
-			goto convert_delay;
-		if (end_fsb > eof_fsb) {
-			end_fsb = eof_fsb;
-			xfs_trim_extent(&imap, offset_fsb,
-					end_fsb - offset_fsb);
+	if (flags & IOMAP_ZERO) {
+		if (isnullstartblock(imap.br_startblock)) {
+			xfs_fileoff_t eof_fsb = XFS_B_TO_FSB(mp, XFS_ISIZE(ip));
+
+			if (offset_fsb >= eof_fsb)
+				goto convert_delay;
+			if (end_fsb > eof_fsb)
+				end_fsb = eof_fsb;
 		}
+		xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);
 	}
 
 	/*
-- 
2.47.0