On Mon, Jun 24, 2019 at 03:55:15PM +0800, Huang, Ying wrote: > From: Huang Ying <[email protected]> > > 0-Day test system reported some OOM regressions for several > THP (Transparent Huge Page) swap test cases. These regressions are > bisected to 6861428921b5 ("block: always define BIO_MAX_PAGES as > 256"). In the commit, BIO_MAX_PAGES is set to 256 even when THP swap > is enabled. So the bio_alloc(gfp_flags, 512) in get_swap_bio() may > fail when swapping out THP. That causes the OOM. > > As in the patch description of 6861428921b5 ("block: always define > BIO_MAX_PAGES as 256"), THP swap should use multi-page bvec to write > THP to swap space. So the issue is fixed via doing that in > get_swap_bio(). > > BTW: I remember I have checked the THP swap code when > 6861428921b5 ("block: always define BIO_MAX_PAGES as 256") was merged, > and thought the THP swap code needn't to be changed. But apparently, > I was wrong. I should have done this at that time. > > Fixes: 6861428921b5 ("block: always define BIO_MAX_PAGES as 256") > Signed-off-by: "Huang, Ying" <[email protected]> > Cc: Ming Lei <[email protected]> > Cc: Michal Hocko <[email protected]> > Cc: Johannes Weiner <[email protected]> > Cc: Hugh Dickins <[email protected]> > Cc: Minchan Kim <[email protected]> > Cc: Rik van Riel <[email protected]> > Cc: Daniel Jordan <[email protected]> > > Changelogs: > > V2: > > - Replace __bio_add_page() with bio_add_page() per Ming's comments. > > --- > mm/page_io.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/mm/page_io.c b/mm/page_io.c > index 2e8019d0e048..189415852077 100644 > --- a/mm/page_io.c > +++ b/mm/page_io.c > @@ -29,10 +29,9 @@ > static struct bio *get_swap_bio(gfp_t gfp_flags, > struct page *page, bio_end_io_t end_io) > { > - int i, nr = hpage_nr_pages(page); > struct bio *bio; > > - bio = bio_alloc(gfp_flags, nr); > + bio = bio_alloc(gfp_flags, 1); > if (bio) { > struct block_device *bdev; > > @@ -41,9 +40,7 @@ static struct bio *get_swap_bio(gfp_t gfp_flags, > bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; > bio->bi_end_io = end_io; > > - for (i = 0; i < nr; i++) > - bio_add_page(bio, page + i, PAGE_SIZE, 0); > - VM_BUG_ON(bio->bi_iter.bi_size != PAGE_SIZE * nr); > + bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0); > } > return bio; > } > -- > 2.20.1 >
Looks fine: Reviewed-by: Ming Lei <[email protected]> Thanks, Ming
