+ mm-memfd_luo-optimize-shmem_recalc_inode-calls-in-retrieve-path.patch added to mm-new branch

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

The patch titled
     Subject: mm/memfd_luo: optimize shmem_recalc_inode calls in retrieve path
has been added to the -mm mm-new branch.  Its filename is
     mm-memfd_luo-optimize-shmem_recalc_inode-calls-in-retrieve-path.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memfd_luo-optimize-shmem_recalc_inode-calls-in-retrieve-path.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_luo: optimize shmem_recalc_inode calls in retrieve path
Date: Mon, 23 Mar 2026 19:07:45 +0800

Move shmem_recalc_inode() out of the loop in memfd_luo_retrieve_folios()
to improve performance when restoring large memfds.

Currently, shmem_recalc_inode() is called for each folio during restore,
which is O(n) expensive operations.  This patch collects the number of
successfully added folios and calls shmem_recalc_inode() once after the
loop completes, reducing complexity to O(1).

Additionally, fix the error path to also call shmem_recalc_inode() for the
folios that were successfully added before the error occurred.

Link: https://lkml.kernel.org/r/20260323110747.193569-3-duanchenghao@kylinos.cn
Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Haoran Jiang <jianghaoran@kylinos.cn>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memfd_luo.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/mm/memfd_luo.c~mm-memfd_luo-optimize-shmem_recalc_inode-calls-in-retrieve-path
+++ a/mm/memfd_luo.c
@@ -410,7 +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;
+	long npages, nr_added_pages = 0;
 	int err = -EIO;
 	long i;
 
@@ -465,12 +465,14 @@ static int memfd_luo_retrieve_folios(str
 			goto unlock_folio;
 		}
 
-		shmem_recalc_inode(inode, npages, 0);
+		nr_added_pages += npages;
 		folio_add_lru(folio);
 		folio_unlock(folio);
 		folio_put(folio);
 	}
 
+	shmem_recalc_inode(inode, nr_added_pages, 0);
+
 	return 0;
 
 unlock_folio:
@@ -489,6 +491,8 @@ put_folios:
 			folio_put(folio);
 	}
 
+	shmem_recalc_inode(inode, nr_added_pages, 0);
+
 	return err;
 }
 
_

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