Commit d6b8f296 authored by Baolin Wang's avatar Baolin Wang Committed by Andrew Morton
Browse files

mm: khugepaged: use the number of pages in the folio to check the reference count 

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: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: default avatarDavid 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent fda6d4de

mm/khugepaged.c

+4 −4
Original line number Diff line number Diff line
@@ -1988,9 +1988,9 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, 
		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_struct *mm, unsigned long addr, 
		 * 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 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, 
		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;