+ mm-khugepaged-use-the-number-of-pages-in-the-folio-to-check-the-reference-count.patch added to mm-unstable branch

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

The patch titled
     Subject: mm: khugepaged: use the number of pages in the folio to check the reference count
has been added to the -mm mm-unstable branch.  Its filename is
     mm-khugepaged-use-the-number-of-pages-in-the-folio-to-check-the-reference-count.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-use-the-number-of-pages-in-the-folio-to-check-the-reference-count.patch

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

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------------------------------------------------------
From: Baolin Wang <baolin.wang@linux.alibaba.com>
Subject: mm: khugepaged: use the number of pages in the folio to check the reference count
Date: Tue, 20 Aug 2024 17:49:14 +0800

Use the number of pages in the folio to check the reference count as
preparation for supporting shmem mTHP collapse.

Link: https://lkml.kernel.org/r/9ea49262308de28957596cc6e8edc2d3a4f54659.1724140601.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Barry Song <21cnbao@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/khugepaged.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/mm/khugepaged.c~mm-khugepaged-use-the-number-of-pages-in-the-folio-to-check-the-reference-count
+++ a/mm/khugepaged.c
@@ -1988,9 +1988,9 @@ static int collapse_file(struct mm_struc
 		VM_BUG_ON_FOLIO(folio != xa_load(xas.xa, index), folio);
 
 		/*
-		 * We control three references to the folio:
+		 * We control 2 + nr_pages references to the folio:
 		 *  - we hold a pin on it;
-		 *  - one reference from page cache;
+		 *  - nr_pages reference from page cache;
 		 *  - one from lru_isolate_folio;
 		 * If those are the only references, then any new usage
 		 * of the folio will have to fetch it from the page
@@ -1998,7 +1998,7 @@ static int collapse_file(struct mm_struc
 		 * truncate, so any new usage will be blocked until we
 		 * unlock folio after collapse/during rollback.
 		 */
-		if (folio_ref_count(folio) != 3) {
+		if (folio_ref_count(folio) != 2 + folio_nr_pages(folio)) {
 			result = SCAN_PAGE_COUNT;
 			xas_unlock_irq(&xas);
 			folio_putback_lru(folio);
@@ -2181,7 +2181,7 @@ immap_locked:
 		folio_clear_active(folio);
 		folio_clear_unevictable(folio);
 		folio_unlock(folio);
-		folio_put_refs(folio, 3);
+		folio_put_refs(folio, 2 + folio_nr_pages(folio));
 	}
 
 	goto out;
_

Patches currently in -mm which might be from baolin.wang@linux.alibaba.com are

mm-shmem-simplify-the-suitable-huge-orders-validation-for-tmpfs.patch
mm-shmem-rename-shmem_is_huge-to-shmem_huge_global_enabled.patch
mm-shmem-move-shmem_huge_global_enabled-into-shmem_allowable_huge_orders.patch
mm-swap-extend-swap_shmem_alloc-to-support-batch-swap_map_shmem-flag-setting.patch
mm-shmem-extend-shmem_partial_swap_usage-to-support-large-folio-swap.patch
mm-filemap-use-xa_get_order-to-get-the-swap-entry-order.patch
mm-shmem-use-swap_free_nr-to-free-shmem-swap-entries.patch
mm-shmem-support-large-folio-allocation-for-shmem_replace_folio.patch
mm-shmem-drop-folio-reference-count-using-nr_pages-in-shmem_delete_from_page_cache.patch
mm-shmem-split-large-entry-if-the-swapin-folio-is-not-large.patch
mm-shmem-support-large-folio-swap-out.patch
mm-khugepaged-expand-the-is_refcount_suitable-to-support-file-folios.patch
mm-khugepaged-use-the-number-of-pages-in-the-folio-to-check-the-reference-count.patch
mm-khugepaged-support-shmem-mthp-copy.patch
mm-khugepaged-support-shmem-mthp-collapse.patch
selftests-mm-support-shmem-mthp-collapse-testing.patch