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authorMiaohe Lin <linmiaohe@huawei.com>2022-06-08 22:40:30 +0800
committerakpm <akpm@linux-foundation.org>2022-07-03 18:08:42 -0700
commitc8945306976f497802b208cf8f2cad4543868bc6 (patch)
tree52be9312a6af5bfc3e1688252c5247060ac89abe /mm/swapfile.c
parent5e21f2d577cf174ced5fe9bdff67dcb70190d9f8 (diff)
mm/swapfile: fix possible data races of inuse_pages
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. READ_ONCE and WRITE_ONCE is used to fix such data races. Note these data races should be ok because they're just used for showing swap info. [linmiaohe@huawei.com: use WRITE_ONCE to pair with READ_ONCE] Link: https://lkml.kernel.org/r/20220625093346.48894-2-linmiaohe@huawei.com 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> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index a2e66d855b19..6a7579951fa4 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -695,7 +695,7 @@ static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
si->lowest_bit += nr_entries;
if (end == si->highest_bit)
WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries);
- si->inuse_pages += nr_entries;
+ WRITE_ONCE(si->inuse_pages, si->inuse_pages + nr_entries);
if (si->inuse_pages == si->pages) {
si->lowest_bit = si->max;
si->highest_bit = 0;
@@ -732,7 +732,7 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
add_to_avail_list(si);
}
atomic_long_add(nr_entries, &nr_swap_pages);
- si->inuse_pages -= nr_entries;
+ WRITE_ONCE(si->inuse_pages, si->inuse_pages - nr_entries);
if (si->flags & SWP_BLKDEV)
swap_slot_free_notify =
si->bdev->bd_disk->fops->swap_slot_free_notify;
@@ -2640,7 +2640,7 @@ static int swap_show(struct seq_file *swap, void *v)
}
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\\");
@@ -3259,7 +3259,7 @@ 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;