Commit 89e8f601 authored by Hugh Dickins's avatar Hugh Dickins Committed by Euler
Browse files

mm: shmem: fix ShmemHugePages at swapout 

mainline inclusion
from mainline-v6.12-rc1
commit dad2dc9c92e0f93f33cebcb0595b8daa3d57473f
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IBGFBA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=dad2dc9c92e0f93f33cebcb0595b8daa3d57473f

--------------------------------

/proc/meminfo ShmemHugePages has been showing overlarge amounts (more than
Shmem) after swapping out THPs: we forgot to update NR_SHMEM_THPS.

Add shmem_update_stats(), to avoid repetition, and risk of making that
mistake again: the call from shmem_delete_from_page_cache() is the bugfix;
the call from shmem_replace_folio() is reassuring, but not really a bugfix
(replace corrects misplaced swapin readahead, but huge swapin readahead
would be a mistake).

Link: https://lkml.kernel.org/r/5ba477c8-a569-70b5-923e-09ab221af45b@google.com


Fixes: 809bc86517cc ("mm: shmem: support large folio swap out")
Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Reviewed-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: default avatarYosry Ahmed <yosryahmed@google.com>
Reviewed-by: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Conflicts:
    mm/shmem.c
[Context conflicts in shmem.c due to miss commit 7aad25b4b47e]
Signed-off-by: default avatarWang Lian <dev01404@linx-info.com>
---
parent 6ac04fc4

mm/shmem.c

+12 −10
Original line number Diff line number Diff line
@@ -773,6 +773,14 @@ static bool shmem_huge_global_enabled(struct inode *inode, pgoff_t index, 
}

#endif /* CONFIG_TRANSPARENT_HUGEPAGE */



static void shmem_update_stats(struct folio *folio, int nr_pages)

{

	if (folio_test_pmd_mappable(folio))

		__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr_pages);

	__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr_pages);

	__lruvec_stat_mod_folio(folio, NR_SHMEM, nr_pages);

}



/*

 * Somewhat like filemap_add_folio, but error if expected item has gone.

 */
@@ -807,10 +815,7 @@ static int shmem_add_to_page_cache(struct folio *folio, 
		xas_store(&xas, folio);

		if (xas_error(&xas))

			goto unlock;

		if (folio_test_pmd_mappable(folio))

			__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr);

		__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);

		__lruvec_stat_mod_folio(folio, NR_SHMEM, nr);

		shmem_update_stats(folio, nr);

		shmem_reliable_folio_add(folio, nr);

		mapping->nrpages += nr;

unlock:
@@ -839,8 +844,7 @@ static void shmem_delete_from_page_cache(struct folio *folio, void *radswap) 
	error = shmem_replace_entry(mapping, folio->index, folio, radswap);

	folio->mapping = NULL;

	mapping->nrpages -= nr;

	__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr);

	__lruvec_stat_mod_folio(folio, NR_SHMEM, -nr);

	shmem_update_stats(folio, -nr);

	shmem_reliable_folio_add(folio, -nr);

	xa_unlock_irq(&mapping->i_pages);

	folio_put_refs(folio, nr);
@@ -1966,11 +1970,9 @@ static int shmem_replace_folio(struct folio **foliop, gfp_t gfp, 
	}

	if (!error) {

		mem_cgroup_replace_folio(old, new);

		__lruvec_stat_mod_folio(new, NR_FILE_PAGES, nr_pages);

		__lruvec_stat_mod_folio(new, NR_SHMEM, nr_pages);

		shmem_update_stats(new, nr_pages);

		shmem_reliable_folio_add(new, nr_pages);

		__lruvec_stat_mod_folio(old, NR_FILE_PAGES, -nr_pages);

		__lruvec_stat_mod_folio(old, NR_SHMEM, -nr_pages);

		shmem_update_stats(old, -nr_pages);

		shmem_reliable_folio_add(old, -nr_pages);

	}

	xa_unlock_irq(&swap_mapping->i_pages);