Sorry for sending a wrong version. Here is new one. >From 2d42ead9335cde51fd58d6348439ca03cf359ba2 Mon Sep 17 00:00:00 2001 From: Minchan Kim <minchan@xxxxxxxxxx> Date: Fri, 11 Nov 2016 15:02:57 +0900 Subject: [PATCH] mm: support anonymous stable page For developemnt for zram-swap asynchronous writeback, I found strange corruption of compressed page. With investigation, it reveals currently stable page doesn't support anonymous page. IOW, reuse_swap_page can reuse the page without waiting writeback completion so that it can corrupt data during zram compression. It can affect every swap device which supports asynchronous writeback and CRC checking as well as zRAM. Unfortunately, reuse_swap_page should be atomic so that we cannot wait on writeback in there so the approach in this patch is simply return false if we found it needs stable page. Although it increases memory footprint temporarily, it happens rarely and it should be reclaimed easily althoug it happened. Also, It would be better than waiting of IO completion, which is critial path for application latency. Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> --- mm/swapfile.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 2210de290b54..ea591435d8e0 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -943,11 +943,21 @@ bool reuse_swap_page(struct page *page, int *total_mapcount) count = page_trans_huge_mapcount(page, total_mapcount); if (count <= 1 && PageSwapCache(page)) { count += page_swapcount(page); - if (count == 1 && !PageWriteback(page)) { + if (count != 1) + goto out; + if (!PageWriteback(page)) { delete_from_swap_cache(page); SetPageDirty(page); + } else { + struct address_space *mapping; + + mapping = page_mapping(page); + if (bdi_cap_stable_pages_required( + inode_to_bdi(mapping->host))) + return false; } } +out: return count <= 1; } @@ -2180,6 +2190,7 @@ static struct swap_info_struct *alloc_swap_info(void) static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) { int error; + struct address_space *swapper_space; if (S_ISBLK(inode->i_mode)) { p->bdev = bdgrab(I_BDEV(inode)); @@ -2202,6 +2213,9 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) } else return -EINVAL; + swapper_space = &swapper_spaces[p->type]; + swapper_space->host = inode; + return 0; } -- 2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>