On Fri, Mar 24, 2017 at 10:00:25AM +0800, Qu Wenruo wrote: > In the following situation, scrub will calculate wrong parity to > overwrite 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 after raid56 read rebuild rbio->stripe_pages are all > correct recovered (0xcd for data stripes). > > However when we check and repair parity, in > scrub_parity_check_and_repair(), we will appending 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.
Reviewed-by: Liu Bo <bo.li....@oracle.com> Thanks, -liubo > > Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com> > --- > fs/btrfs/scrub.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c > index 6832feece7a7..2a5458004279 100644 > --- a/fs/btrfs/scrub.c > +++ b/fs/btrfs/scrub.c > @@ -2957,7 +2957,6 @@ 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; > @@ -2987,9 +2986,6 @@ 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; > -- > 2.12.1 > > > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
