[PATCH] fix unsuccessful folio2 split

[Zi Yan]

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
 mm/truncate.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/mm/truncate.c b/mm/truncate.c
index b58ba940be474..2c575f5e61889 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -259,6 +259,7 @@ bool truncate_inode_partial_folio(struct folio *folio, =
loff_t start, loff_t end)
 		 * for shmem truncate
 		 */
 		struct folio *folio2;
+		bool ret =3D true;
=20
 		if (offset + length =3D=3D size)
 			goto no_split;
@@ -273,19 +274,23 @@ bool truncate_inode_partial_folio(struct folio *folio=
, loff_t start, loff_t end)
 		if (!folio_test_large(folio2))
 			goto out;
=20
-		if (!folio_trylock(folio2))
+		if (!folio_trylock(folio2)) {
+			ret =3D false;
 			goto out;
+		}
=20
 		/* make sure folio2 is large and does not change its mapping */
 		if (folio_test_large(folio2) &&
 		    folio2->mapping =3D=3D folio->mapping)
-			folio_split_or_unmap(folio2, split_at2, min_order);
+			ret =3D !folio_split_or_unmap(folio2, split_at2, min_order);
+		else
+			ret =3D false;
=20
 		folio_unlock(folio2);
 out:
 		folio_put(folio2);
 no_split:
-		return true;
+		return ret;
 	}
 	if (folio_test_dirty(folio))
 		return false;
--=20
2.53.0


>
>   - Add an optional out-parameter pgoff_t *end, set to the index of the
>     folio that contains @lend and must be kept by the caller's loop. It
>     is only written when the folio actually straddles @lend. On the
>     success path it defaults to the page index of the end edge and is
>     refined to folio2->index when the second split fails to isolate the
>     tail.
>
>   - Rename the byte-range parameters start/end to lstart/lend to avoid
>     clashing with the new @end output and to separate byte offsets from
>     folio indices.
>
> Callers in truncate_inode_pages_range() and shmem_undo_range() pass &end
> only when the folio straddles lend. After all, no caller discards a
> straddling folio anymore, the in-range cleanly-split sub-folios below it
> are still dropped.
>
> Suggested-by: Brian Foster <bfoster@xxxxxxxxxx>
> Link: https://lore.kernel.org/linux-fsdevel/anH-WKA1coW6wtfG@bfoster/
> Fixes: 7460b470a131 ("mm/truncate: use folio_split() in truncate operatio=
n")
> Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
> ---
>  mm/internal.h |  4 ++--
>  mm/shmem.c    | 12 +++++------
>  mm/truncate.c | 57 ++++++++++++++++++++++++++++++---------------------
>  3 files changed, 41 insertions(+), 32 deletions(-)
>


--=20
Best Regards,
Yan, Zi