+ mm-swap-move-nr_swap_pages-counter-decrement-from-folio_alloc_swap-to-swap_range_alloc.patch added to mm-new branch

+ mm-swap-move-nr_swap_pages-counter-decrement-from-folio_alloc_swap-to-swap_range_alloc.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm: swap: move nr_swap_pages counter decrement from folio_alloc_swap() to swap_range_alloc()
has been added to the -mm mm-new branch.  Its filename is
     mm-swap-move-nr_swap_pages-counter-decrement-from-folio_alloc_swap-to-swap_range_alloc.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swap-move-nr_swap_pages-counter-decrement-from-folio_alloc_swap-to-swap_range_alloc.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.

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------------------------------------------------------
From: Kemeng Shi <shikemeng@huaweicloud.com>
Subject: mm: swap: move nr_swap_pages counter decrement from folio_alloc_swap() to swap_range_alloc()
Date: Thu, 22 May 2025 20:25:51 +0800

Patch series "Some randome fixes and cleanups to swapfile".

Patch 0-3 are some random fixes.  Patch 4 is a cleanup.  More details can
be found in respective patches.


This patch (of 4):

When folio_alloc_swap() encounters a failure in either
mem_cgroup_try_charge_swap() or add_to_swap_cache(), nr_swap_pages counter
is not decremented for allocated entry.  However, the following
put_swap_folio() will increase nr_swap_pages counter unpairly and lead to
an imbalance.

Move nr_swap_pages decrement from folio_alloc_swap() to swap_range_alloc()
to pair the nr_swap_pages counting.

Link: https://lkml.kernel.org/r/20250522122554.12209-1-shikemeng@huaweicloud.com
Link: https://lkml.kernel.org/r/20250522122554.12209-2-shikemeng@huaweicloud.com
Fixes: 0ff67f990bd45 ("mm, swap: remove swap slot cache")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Kairui Song <kasong@tencent.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/swapfile.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/swapfile.c~mm-swap-move-nr_swap_pages-counter-decrement-from-folio_alloc_swap-to-swap_range_alloc
+++ a/mm/swapfile.c
@@ -1115,6 +1115,7 @@ static void swap_range_alloc(struct swap
 		if (vm_swap_full())
 			schedule_work(&si->reclaim_work);
 	}
+	atomic_long_sub(nr_entries, &nr_swap_pages);
 }
 
 static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
@@ -1313,7 +1314,6 @@ int folio_alloc_swap(struct folio *folio
 	if (add_to_swap_cache(folio, entry, gfp | __GFP_NOMEMALLOC, NULL))
 		goto out_free;
 
-	atomic_long_sub(size, &nr_swap_pages);
 	return 0;
 
 out_free:
_

Patches currently in -mm which might be from shikemeng@huaweicloud.com are

mm-shmem-avoid-unpaired-folio_unlock-in-shmem_swapin_folio.patch
mm-shmem-add-missing-shmem_unacct_size-in-__shmem_file_setup.patch
mm-shmem-fix-potential-dead-loop-in-shmem_unuse.patch
mm-shmem-only-remove-inode-from-swaplist-when-its-swapped-page-count-is-0.patch
mm-shmem-remove-unneeded-xa_is_value-check-in-shmem_unuse_swap_entries.patch
mm-swap-move-nr_swap_pages-counter-decrement-from-folio_alloc_swap-to-swap_range_alloc.patch
mm-swap-correctly-use-maxpages-in-swapon-syscall-to-avoid-potensial-deadloop.patch
mm-swap-fix-potensial-buffer-overflow-in-setup_clusters.patch
mm-swap-remove-stale-comment-stale-comment-in-cluster_alloc_swap_entry.patch