[PATCH 6.12.y] f2fs: fix to check continuousness in f2fs_sync_meta_pages() correctly

[Sasha Levin <sashal@kernel.org>]

From: Chao Yu <chao@kernel.org>

[ Upstream commit 1383cff4ccf3c8833c6255edffa29eb67c6419bb ]

In f2fs_sync_meta_pages(), whenever i becomes zero inside while loop,
below check may be skipped, it failed to check the continuousness:

	if (nr_to_write != LONG_MAX && i != 0 &&
		folio->index != prev +
		folio_nr_pages(fbatch.folios[i-1])) {

Cc: stable@kernel.org
Fixes: 580e7a492608 ("f2fs: convert f2fs_sync_meta_pages() to use filemap_get_folios_tag()")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
[ sashal: adapted the cached-block check to folio-based f2fs_sync_meta_pages(), using nr_to_write instead of background and folio_nr_pages() for index increments ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/f2fs/checkpoint.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index dc9540400caae..eb928d644542f 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -423,7 +423,7 @@ long f2fs_sync_meta_pages(struct f2fs_sb_info *sbi, enum page_type type,
 				long nr_to_write, enum iostat_type io_type)
 {
 	struct address_space *mapping = META_MAPPING(sbi);
-	pgoff_t index = 0, prev = ULONG_MAX;
+	pgoff_t index = 0, next = ULONG_MAX;
 	struct folio_batch fbatch;
 	long nwritten = 0;
 	int nr_folios;
@@ -444,9 +444,8 @@ long f2fs_sync_meta_pages(struct f2fs_sb_info *sbi, enum page_type type,
 		for (i = 0; i < nr_folios; i++) {
 			struct folio *folio = fbatch.folios[i];
 
-			if (nr_to_write != LONG_MAX && i != 0 &&
-					folio->index != prev +
-					folio_nr_pages(fbatch.folios[i-1])) {
+			if (nr_to_write != LONG_MAX && next != ULONG_MAX &&
+					folio->index != next) {
 				folio_batch_release(&fbatch);
 				goto stop;
 			}
@@ -475,7 +474,7 @@ long f2fs_sync_meta_pages(struct f2fs_sb_info *sbi, enum page_type type,
 				break;
 			}
 			nwritten += folio_nr_pages(folio);
-			prev = folio->index;
+			next = folio->index + folio_nr_pages(folio);
 			if (unlikely(nwritten >= nr_to_write))
 				break;
 		}
-- 
2.53.0