diff options
| -rw-r--r-- | mm/vmscan.c | 33 |
1 files changed, 24 insertions, 9 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index ca43aa00ea0..e37e6872509 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -723,23 +723,38 @@ static unsigned long shrink_page_list(struct list_head *page_list, /* * memcg doesn't have any dirty pages throttling so we * could easily OOM just because too many pages are in - * writeback from reclaim and there is nothing else to - * reclaim. + * writeback and there is nothing else to reclaim. * - * Check may_enter_fs, certainly because a loop driver + * Check __GFP_IO, certainly because a loop driver * thread might enter reclaim, and deadlock if it waits * on a page for which it is needed to do the write * (loop masks off __GFP_IO|__GFP_FS for this reason); * but more thought would probably show more reasons. + * + * Don't require __GFP_FS, since we're not going into + * the FS, just waiting on its writeback completion. + * Worryingly, ext4 gfs2 and xfs allocate pages with + * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so + * testing may_enter_fs here is liable to OOM on them. */ - if (!global_reclaim(sc) && PageReclaim(page) && - may_enter_fs) - wait_on_page_writeback(page); - else { + if (global_reclaim(sc) || + !PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) { + /* + * This is slightly racy - end_page_writeback() + * might have just cleared PageReclaim, then + * setting PageReclaim here end up interpreted + * as PageReadahead - but that does not matter + * enough to care. What we do want is for this + * page to have PageReclaim set next time memcg + * reclaim reaches the tests above, so it will + * then wait_on_page_writeback() to avoid OOM; + * and it's also appropriate in global reclaim. + */ + SetPageReclaim(page); nr_writeback++; - unlock_page(page); - goto keep; + goto keep_locked; } + wait_on_page_writeback(page); } references = page_check_references(page, sc); |