diff options
| author | Miaohe Lin <linmiaohe@huawei.com> | 2022-06-08 22:40:30 +0800 |
|---|---|---|
| committer | akpm <akpm@linux-foundation.org> | 2022-07-03 18:08:42 -0700 |
| commit | c8945306976f497802b208cf8f2cad4543868bc6 (patch) | |
| tree | 52be9312a6af5bfc3e1688252c5247060ac89abe /mm/swapfile.c | |
| parent | 5e21f2d577cf174ced5fe9bdff67dcb70190d9f8 (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.c | 8 |
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; |