+ mm-truncate-clarify-return-value-of-truncate_inode_partial_folio.patch added to mm-new branch

+ mm-truncate-clarify-return-value-of-truncate_inode_partial_folio.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/truncate: clarify return value of truncate_inode_partial_folio()
has been added to the -mm mm-new branch.  Its filename is
     mm-truncate-clarify-return-value-of-truncate_inode_partial_folio.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-truncate-clarify-return-value-of-truncate_inode_partial_folio.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Zhang Yi <yi.zhang@huawei.com>
Subject: mm/truncate: clarify return value of truncate_inode_partial_folio()
Date: Mon, 28 Sep 2026 20:08:33 +0800

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.

Link: https://lore.kernel.org/20260928120833.3440834-5-yi.zhang@huaweicloud.com
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Joanne Koong <joannelkoong@gmail.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: <yizhang089@gmail.com>
Cc: Yang Erkun <yangerkun@huawei.com>
Cc: Zhihao Cheng <chengzhihao1@huawei.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: <yukuai@fnnas.com>
---

 mm/truncate.c |   14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

--- a/mm/truncate.c~mm-truncate-clarify-return-value-of-truncate_inode_partial_folio
+++ a/mm/truncate.c
@@ -216,8 +216,7 @@ static int folio_split_or_unmap(struct f
  * 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_wait_writeback(folio);
 	if (length == size) {
 		truncate_inode_folio(folio->mapping, folio);
-		return true;
+		return false;
 	}
 
 	/*
@@ -264,7 +263,7 @@ bool truncate_inode_partial_folio(struct
 	min_order = mapping_min_folio_order(folio->mapping);
 	min_nrbytes = mapping_min_folio_nrbytes(folio->mapping);
 	if (folio_order(folio) == min_order)
-		return true;
+		return false;
 
 	split_at = folio_page(folio, PAGE_ALIGN_DOWN(offset) / PAGE_SIZE);
 	if (!folio_split_or_unmap(folio, split_at, min_order)) {
@@ -327,10 +326,9 @@ out:
 			*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;
 }
 
 /*
_

Patches currently in -mm which might be from yi.zhang@huawei.com are

mm-truncate-align-truncation-boundaries-to-mapping-minimum-folio-order.patch
mm-truncate-look-up-the-end-edge-straddler-by-index.patch
mm-truncate-fix-data-loss-when-splitting-straddling-large-folios-fails.patch
mm-truncate-clarify-return-value-of-truncate_inode_partial_folio.patch