From 9a33944bdf075ca93062cde206cb25e62044890e Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Wed, 29 Mar 2017 09:33:20 +0800 Subject: [PATCH] btrfs: scrub: Don't append on-disk pages for raid56 scrub In the following situation, scrub will calculate wrong parity to overwrite the correct one: RAID5 full stripe: Before | Dev 1 | Dev 2 | Dev 3 | | Data stripe 1 | Data stripe 2 | Parity Stripe | --------------------------------------------------- 0 | 0x0000 (Bad) | 0xcdcd | 0x0000 | --------------------------------------------------- 4K | 0xcdcd | 0xcdcd | 0x0000 | ... | 0xcdcd | 0xcdcd | 0x0000 | --------------------------------------------------- 64K After scrubbing dev3 only: | Dev 1 | Dev 2 | Dev 3 | | Data stripe 1 | Data stripe 2 | Parity Stripe | --------------------------------------------------- 0 | 0xcdcd (Good) | 0xcdcd | 0xcdcd (Bad) | --------------------------------------------------- 4K | 0xcdcd | 0xcdcd | 0x0000 | ... | 0xcdcd | 0xcdcd | 0x0000 | --------------------------------------------------- 64K The reason is that after raid56 read rebuild rbio->stripe_pages are all correctly recovered (0xcd for data stripes). However when we check and repair parity in scrub_parity_check_and_repair(), we will append pages in sparity->spages list to rbio->bio_pages[], which contains old on-disk data. And when we submit parity data to disk, we calculate parity using rbio->bio_pages[] first, if rbio->bio_pages[] not found, then fallback to rbio->stripe_pages[]. The patch fix it by not appending pages from sparity->spages. So finish_parity_scrub() will use rbio->stripe_pages[] which is correct. Signed-off-by: Qu Wenruo Reviewed-by: Liu Bo Signed-off-by: David Sterba --- fs/btrfs/scrub.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c index fe1c793877dd..26dbe563fed0 100644 --- a/fs/btrfs/scrub.c +++ b/fs/btrfs/scrub.c @@ -2769,7 +2769,6 @@ static void scrub_parity_check_and_repair(struct scrub_parity *sparity) struct btrfs_fs_info *fs_info = sctx->fs_info; struct bio *bio; struct btrfs_raid_bio *rbio; - struct scrub_page *spage; struct btrfs_bio *bbio = NULL; u64 length; int ret; @@ -2799,9 +2798,6 @@ static void scrub_parity_check_and_repair(struct scrub_parity *sparity) if (!rbio) goto rbio_out; - list_for_each_entry(spage, &sparity->spages, list) - raid56_add_scrub_pages(rbio, spage->page, spage->logical); - scrub_pending_bio_inc(sctx); raid56_parity_submit_scrub_rbio(rbio); return; -- 2.20.1