[PATCH v4 4/4] mm/truncate: clarify return value of truncate_inode_partial_folio()

[Zhang Yi]

From: Zhang Yi <yi.zhang@xxxxxxxxxx>

With the earlier rework the callers no longer rely on the return value
of truncate_inode_partial_folio() to decide whether to adjust the
truncation range. The pstart/pend out-parameters carry that information
instead. The callers now only use the return value as a flag indicating
whether the loop should be reset to pick up newly split sub-folios on
the shmem path.

Return true if at least one split succeeded, and false otherwise.
This clarifies the existing confusing return value semantics.

Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
 mm/truncate.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/mm/truncate.c b/mm/truncate.c
index 81fb4de6226b..317cb4ae3625 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -216,8 +216,7 @@ static int folio_split_or_unmap(struct folio *folio, struct page *split_at,
  * aligned inwards to min_order, i.e. the range of folios wholly within
  * [lstart, lend] and so safe to discard.
  *
- * Returns false if splitting failed so the caller can avoid
- * discarding the entire folio which is stubbornly unsplit.
+ * Return %true if at least one split succeeded, %false otherwise.
  */
 bool truncate_inode_partial_folio(struct folio *folio, loff_t lstart,
 				  loff_t lend, pgoff_t *pstart, pgoff_t *pend)
@@ -247,7 +246,7 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t lstart,
 	folio_wait_writeback(folio);
 	if (length == size) {
 		truncate_inode_folio(folio->mapping, folio);
-		return true;
+		return false;
 	}
 
 	/*
@@ -261,7 +260,7 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t lstart,
 	if (folio_needs_release(folio))
 		folio_invalidate(folio, offset, length);
 	if (!folio_test_large(folio))
-		return true;
+		return false;
 
 	min_order = mapping_min_folio_order(folio->mapping);
 	min_nrbytes = mapping_min_folio_nrbytes(folio->mapping);
@@ -326,10 +325,9 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t lstart,
 			*pend = end;
 		return true;
 	}
-	if (folio_test_dirty(folio))
-		return false;
-	truncate_inode_folio(folio->mapping, folio);
-	return true;
+	if (!folio_test_dirty(folio))
+		truncate_inode_folio(folio->mapping, folio);
+	return false;
 }
 
 /*
-- 
2.52.0