| Message ID | 20220527092626.31883-4-linmiaohe@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | A few fixup patches for swap | expand |
On 27.05.22 11:26, Miaohe Lin wrote: > 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. > > Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> > --- > mm/swapfile.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index e033a53a99df..29d7ca9eaa3c 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -2649,7 +2649,7 @@ 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\\"); > @@ -3268,7 +3268,7 @@ 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; AFAIKT, this makes sense Reviewed-by: David Hildenbrand <david@redhat.com>
diff --git a/mm/swapfile.c b/mm/swapfile.c index e033a53a99df..29d7ca9eaa3c 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2649,7 +2649,7 @@ 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\\"); @@ -3268,7 +3268,7 @@ 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;
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. Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> --- mm/swapfile.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)