+ mm-memfd-use-folio_nr_pages-for-shmem-inode-accounting.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/memfd: use folio_nr_pages() for shmem inode accounting
has been added to the -mm mm-new branch.  Its filename is
     mm-memfd-use-folio_nr_pages-for-shmem-inode-accounting.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memfd-use-folio_nr_pages-for-shmem-inode-accounting.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: Chenghao Duan <duanchenghao@kylinos.cn>
Subject: mm/memfd: use folio_nr_pages() for shmem inode accounting
Date: Thu, 26 Mar 2026 16:47:21 +0800

Patch series "Modify memfd_luo code", v3.

memfd_luo_retrieve_folios() called shmem_inode_acct_blocks() and
shmem_recalc_inode() with hardcoded 1 instead of the actual folio page
count.  memfd may use large folios (THP/hugepages), causing quota/limit
under-accounting and incorrect stat output.

Fix by using folio_nr_pages(folio) for both functions.

Issue found by AI review and suggested by Pratyush Yadav <pratyush@kernel.org>.
https://sashiko.dev/#/patchset/20260319012845.29570-1-duanchenghao%40kylinos.cn

Link: https://lkml.kernel.org/r/20260326084727.118437-1-duanchenghao@kylinos.cn
Link: https://lkml.kernel.org/r/20260326084727.118437-2-duanchenghao@kylinos.cn
Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
Suggested-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Haoran Jiang <jianghaoran@kylinos.cn>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memfd_luo.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/mm/memfd_luo.c~mm-memfd-use-folio_nr_pages-for-shmem-inode-accounting
+++ a/mm/memfd_luo.c
@@ -410,6 +410,7 @@ static int memfd_luo_retrieve_folios(str
 	struct inode *inode = file_inode(file);
 	struct address_space *mapping = inode->i_mapping;
 	struct folio *folio;
+	long npages;
 	int err = -EIO;
 	long i;
 
@@ -456,14 +457,15 @@ static int memfd_luo_retrieve_folios(str
 		if (flags & MEMFD_LUO_FOLIO_DIRTY)
 			folio_mark_dirty(folio);
 
-		err = shmem_inode_acct_blocks(inode, 1);
+		npages = folio_nr_pages(folio);
+		err = shmem_inode_acct_blocks(inode, npages);
 		if (err) {
-			pr_err("shmem: failed to account folio index %ld: %d\n",
-			       i, err);
+			pr_err("shmem: failed to account folio index %ld(%ld pages): %d\n",
+			       i, npages, err);
 			goto unlock_folio;
 		}
 
-		shmem_recalc_inode(inode, 1, 0);
+		shmem_recalc_inode(inode, npages, 0);
 		folio_add_lru(folio);
 		folio_unlock(folio);
 		folio_put(folio);
_

Patches currently in -mm which might be from duanchenghao@kylinos.cn are

mm-memfd-use-folio_nr_pages-for-shmem-inode-accounting.patch
mm-memfd_luo-optimize-shmem_recalc_inode-calls-in-retrieve-path.patch
mm-memfd_luo-remove-unnecessary-memset-in-zero-size-memfd-path.patch
mm-memfd_luo-use-i_size_write-to-set-inode-size-during-retrieve.patch
mm-memfd_luo-fix-physical-address-conversion-in-put_folios-cleanup.patch
mm-memfd_luo-remove-folio-from-page-cache-when-accounting-fails.patch
mm-memfd_luo-fix-integer-overflow-in-memfd_luo_preserve_folios.patch