+ mm-swapfile-fix-possible-data-races-of-inuse_pages.patch added to mm-unstable branch

+ mm-swapfile-fix-possible-data-races-of-inuse_pages.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/swapfile: fix possible data races of inuse_pages
has been added to the -mm mm-unstable branch.  Its filename is
     mm-swapfile-fix-possible-data-races-of-inuse_pages.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swapfile-fix-possible-data-races-of-inuse_pages.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: Miaohe Lin <linmiaohe@huawei.com>
Subject: mm/swapfile: fix possible data races of inuse_pages
Date: Wed, 8 Jun 2022 22:40:30 +0800

si->inuse_pages could still be accessed concurrently now.  The plain reads
outside si->lock critical section, i.e.  swap_show and si_swapinfo, which
results in data races.  But these should be ok because they're just used
for showing swap info.

Link: https://lkml.kernel.org/r/20220608144031.829-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/swapfile.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/swapfile.c~mm-swapfile-fix-possible-data-races-of-inuse_pages
+++ a/mm/swapfile.c
@@ -2646,7 +2646,7 @@ static int swap_show(struct seq_file *sw
 	}
 
 	bytes = si->pages << (PAGE_SHIFT - 10);
-	inuse = si->inuse_pages << (PAGE_SHIFT - 10);
+	inuse = READ_ONCE(si->inuse_pages) << (PAGE_SHIFT - 10);
 
 	file = si->swap_file;
 	len = seq_file_path(swap, file, " \t\n\\");
@@ -3265,7 +3265,7 @@ void si_swapinfo(struct sysinfo *val)
 		struct swap_info_struct *si = swap_info[type];
 
 		if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
-			nr_to_be_unused += si->inuse_pages;
+			nr_to_be_unused += READ_ONCE(si->inuse_pages);
 	}
 	val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
 	val->totalswap = total_swap_pages + nr_to_be_unused;
_

Patches currently in -mm which might be from linmiaohe@huawei.com are

maintainers-add-myself-as-a-memory-failure-reviewer.patch
mm-shmemc-clean-up-comment-of-shmem_swapin_folio.patch
mm-reduce-the-rcu-lock-duration.patch
mm-migration-remove-unneeded-lock-page-and-pagemovable-check.patch
mm-migration-return-errno-when-isolate_huge_page-failed.patch
mm-migration-fix-potential-pte_unmap-on-an-not-mapped-pte.patch
mm-memremap-fix-wrong-function-name-above-memremap_pages.patch
mm-swapfile-make-security_vm_enough_memory_mm-work-as-expected.patch
mm-swapfile-fix-possible-data-races-of-inuse_pages.patch
mm-swap-remove-swap_cache_info-statistics.patch