iomap: fix incorrect did_zero setting in iomap_zero_iter()

The did_zero output parameter was unconditionally set after the loop,
which is incorrect. It should only be set when the zeroing operation
actually completes, not when IOMAP_F_STALE is set or when
IOMAP_F_FOLIO_BATCH is set but !folio causes the loop to break early,
or when iomap_iter_advance() returns an error.

This causes did_zero to be incorrectly set when zeroing a clean
unwritten extent because the loop exits early without actually zeroing
any data.

Fix it by using a local variable to track whether any folio was actually
zeroed, and only set did_zero after the loop if zeroing happened.

Fixes: 98eb8d95025b ("iomap: set did_zero to true when zeroing successfully")
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20260714082325.325163-4-yi.zhang@huaweicloud.com
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index b482e112321f307d236793a3ea374d1a0092038c..0cf62e516827a6f2154b46c71f29bc7e0d592933 100644 (file)
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1625,6 +1625,7 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero,
                const struct iomap_write_ops *write_ops)
 {
        u64 bytes = iomap_length(iter);
+       bool zeroed = false;
        int status;
 
        do {
@@ -1645,6 +1646,8 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero,
                /* a NULL folio means we're done with a folio batch */
                if (!folio) {
                        status = iomap_iter_advance_full(iter);
+                       if (status)
+                               return status;
                        break;
                }
 
@@ -1655,6 +1658,7 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero,
                                bytes);
 
                folio_zero_range(folio, offset, bytes);
+               zeroed = true;
                folio_mark_accessed(folio);
 
                ret = iomap_write_end(iter, bytes, bytes, folio);
@@ -1664,10 +1668,10 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero,
 
                status = iomap_iter_advance(iter, bytes);
                if (status)
-                       break;
+                       return status;
        } while ((bytes = iomap_length(iter)) > 0);
 
-       if (did_zero)
+       if (did_zero && zeroed)
                *did_zero = true;
        return status;
 }