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-rw-r--r--fs/iomap/buffered-io.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index ae8673ce08b1..0350830fc989 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -640,11 +640,13 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
size_t poff, plen;
/*
- * If the write completely overlaps the current folio, then
+ * If the write or zeroing completely overlaps the current folio, then
* entire folio will be dirtied so there is no need for
* per-block state tracking structures to be attached to this folio.
+ * For the unshare case, we must read in the ondisk contents because we
+ * are not changing pagecache contents.
*/
- if (pos <= folio_pos(folio) &&
+ if (!(iter->flags & IOMAP_UNSHARE) && pos <= folio_pos(folio) &&
pos + len >= folio_pos(folio) + folio_size(folio))
return 0;