From: Huang Ying ying.huang@intel.com Subject: mm, swap: fix THP swap out
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.
Link: http://lkml.kernel.org/r/20190624075515.31040-1-ying.huang@intel.com Fixes: 6861428921b5 ("block: always define BIO_MAX_PAGES as 256") Signed-off-by: "Huang, Ying" ying.huang@intel.com Reviewed-by: Ming Lei ming.lei@redhat.com Cc: Michal Hocko mhocko@kernel.org Cc: Johannes Weiner hannes@cmpxchg.org Cc: Hugh Dickins hughd@google.com Cc: Minchan Kim minchan@kernel.org Cc: Rik van Riel riel@redhat.com Cc: Daniel Jordan daniel.m.jordan@oracle.com Cc: Jens Axboe axboe@kernel.dk Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/page_io.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
--- a/mm/page_io.c~mm-swap-fix-thp-swap-out +++ a/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 gf 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; } _