Currently, we no longer attempt to write back filesystem folios in pageout(),
and only tmpfs/shmem folios and anonymous swapcache folios can be written back.
Moreover, tmpfs/shmem and swapcache folios do not use the PG_private flag,
which means no fs-private private data is used. Therefore, we can remove the
redundant folio_test_private() checks and related buffer_head release logic.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 mm/vmscan.c | 16 +---------------
 1 file changed, 1 insertion(+), 15 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f1fc36729ddd..8056fccb9cc4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -697,22 +697,8 @@ static pageout_t pageout(struct folio *folio, struct address_space *mapping,
 	 * swap_backing_dev_info is bust: it doesn't reflect the
 	 * congestion state of the swapdevs.  Easy to fix, if needed.
 	 */
-	if (!is_page_cache_freeable(folio))
+	if (!is_page_cache_freeable(folio) || !mapping)
 		return PAGE_KEEP;
-	if (!mapping) {
-		/*
-		 * Some data journaling orphaned folios can have
-		 * folio->mapping == NULL while being dirty with clean buffers.
-		 */
-		if (folio_test_private(folio)) {
-			if (try_to_free_buffers(folio)) {
-				folio_clear_dirty(folio);
-				pr_info("%s: orphaned folio\n", __func__);
-				return PAGE_CLEAN;
-			}
-		}
-		return PAGE_KEEP;
-	}
 
 	if (!shmem_mapping(mapping) && !folio_test_anon(folio))
 		return PAGE_ACTIVATE;
-- 
2.43.7


Since we no longer attempt to write back filesystem folios in pageout(),
and only tmpfs/shmem folios and anonymous swapcache folios can be written
back, we can remove the redundant folio_test_private() when checking the
folio's refcount, as tmpfs/shmem and swapcache folios do not use the
PG_private flag.

While we're at it, we can open-code the folio refcount check instead of
adding a simple helper that has only one user.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 mm/vmscan.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8056fccb9cc4..46baaadc528d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -477,17 +477,6 @@ static int reclaimer_offset(struct scan_control *sc)
 	return PGSTEAL_DIRECT - PGSTEAL_KSWAPD;
 }
 
-static inline int is_page_cache_freeable(struct folio *folio)
-{
-	/*
-	 * A freeable page cache folio is referenced only by the caller
-	 * that isolated the folio, the page cache and optional filesystem
-	 * private data at folio->private.
-	 */
-	return folio_ref_count(folio) - folio_test_private(folio) ==
-		1 + folio_nr_pages(folio);
-}
-
 /*
  * We detected a synchronous write error writing a folio out.  Probably
  * -ENOSPC.  We need to propagate that into the address_space for a subsequent
@@ -696,8 +685,11 @@ static pageout_t pageout(struct folio *folio, struct address_space *mapping,
 	 * block, for some throttling. This happens by accident, because
 	 * swap_backing_dev_info is bust: it doesn't reflect the
 	 * congestion state of the swapdevs.  Easy to fix, if needed.
+	 *
+	 * A freeable shmem or swapcache folio is referenced only by the
+	 * caller that isolated the folio and the page cache.
 	 */
-	if (!is_page_cache_freeable(folio) || !mapping)
+	if (folio_ref_count(folio) != 1 + folio_nr_pages(folio) || !mapping)
 		return PAGE_KEEP;
 
 	if (!shmem_mapping(mapping) && !folio_test_anon(folio))
-- 
2.43.7