[PATCH RFCv2 4/4] xfs: fill dirty folios on zero range of unwritten mappings

[Brian Foster <bfoster@redhat.com>]

Use the iomap folio batch mechanism to identify which folios to zero
on zero range of unwritten mappings. Trim the resulting mapping if
the batch is filled (unlikely) and set the HAS_FOLIOS flag to inform
iomap that pagecache has been checked for dirty folios.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/xfs/xfs_iomap.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 97fa860a6401..b7dbd34fc02f 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -998,6 +998,7 @@ xfs_buffered_write_iomap_begin(
 	struct iomap		*iomap,
 	struct iomap		*srcmap)
 {
+	struct iomap_iter	*iter = container_of(iomap, struct iomap_iter, iomap);
 	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);
@@ -1065,12 +1066,21 @@ xfs_buffered_write_iomap_begin(
 	 */
 	if (flags & IOMAP_ZERO) {
 		xfs_fileoff_t eof_fsb = XFS_B_TO_FSB(mp, XFS_ISIZE(ip));
+		u64 end;
 
 		if (isnullstartblock(imap.br_startblock) &&
 		    offset_fsb >= eof_fsb)
 			goto convert_delay;
 		if (offset_fsb < eof_fsb && end_fsb > eof_fsb)
 			end_fsb = eof_fsb;
+		if (imap.br_state == XFS_EXT_UNWRITTEN &&
+		    offset_fsb < eof_fsb) {
+			xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);
+			end = iomap_fill_dirty_folios(iter,
+					XFS_FSB_TO_B(mp, imap.br_startoff),
+					XFS_FSB_TO_B(mp, imap.br_blockcount));
+			end_fsb = min_t(xfs_fileoff_t, end_fsb, XFS_B_TO_FSB(mp, end));
+		}
 
 		xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);
 	}
-- 
2.47.0