On Fri, Mar 24, 2017 at 10:00:27AM +0800, Qu Wenruo wrote:
> Unlike other place calling btrfs_map_block(), in raid56 scrub, we don't
> use bio_counter to protect from race against dev replace.
>
> This patch will use bio_counter to protect from the beginning of calling
> btrfs_map_sblock(), until rbio endio.
>
> Liu Bo <bo.li.liu@xxxxxxxxxx>
> Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/raid56.c | 2 ++
> fs/btrfs/scrub.c | 5 +++++
> 2 files changed, 7 insertions(+)
>
> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> index 1571bf26dc07..3a083165400f 100644
> --- a/fs/btrfs/raid56.c
> +++ b/fs/btrfs/raid56.c
> @@ -2642,6 +2642,7 @@ static void async_scrub_parity(struct btrfs_raid_bio *rbio)
>
> void raid56_parity_submit_scrub_rbio(struct btrfs_raid_bio *rbio)
> {
> + rbio->generic_bio_cnt = 1;
To keep consistent with other places, can you please do this setting when
allocating rbio?
> if (!lock_stripe_add(rbio))
> async_scrub_parity(rbio);
> }
> @@ -2694,6 +2695,7 @@ static void async_missing_raid56(struct btrfs_raid_bio *rbio)
>
> void raid56_submit_missing_rbio(struct btrfs_raid_bio *rbio)
> {
> + rbio->generic_bio_cnt = 1;
> if (!lock_stripe_add(rbio))
> async_missing_raid56(rbio);
> }
Ditto.
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 2a5458004279..265387bf3af8 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -2379,6 +2379,7 @@ static void scrub_missing_raid56_pages(struct scrub_block *sblock)
> int ret;
> int i;
>
> + btrfs_bio_counter_inc_blocked(fs_info);
> ret = btrfs_map_sblock(fs_info, BTRFS_MAP_GET_READ_MIRRORS, logical,
> &length, &bbio, 0, 1);
> if (ret || !bbio || !bbio->raid_map)
> @@ -2423,6 +2424,7 @@ static void scrub_missing_raid56_pages(struct scrub_block *sblock)
> rbio_out:
> bio_put(bio);
> bbio_out:
> + btrfs_bio_counter_dec(fs_info);
> btrfs_put_bbio(bbio);
> spin_lock(&sctx->stat_lock);
> sctx->stat.malloc_errors++;
> @@ -2966,6 +2968,8 @@ static void scrub_parity_check_and_repair(struct scrub_parity *sparity)
> goto out;
>
> length = sparity->logic_end - sparity->logic_start;
> +
> + btrfs_bio_counter_inc_blocked(fs_info);
> ret = btrfs_map_sblock(fs_info, BTRFS_MAP_WRITE, sparity->logic_start,
> &length, &bbio, 0, 1);
> if (ret || !bbio || !bbio->raid_map)
> @@ -2993,6 +2997,7 @@ static void scrub_parity_check_and_repair(struct scrub_parity *sparity)
> rbio_out:
> bio_put(bio);
> bbio_out:
> + btrfs_bio_counter_dec(fs_info);
> btrfs_put_bbio(bbio);
> bitmap_or(sparity->ebitmap, sparity->ebitmap, sparity->dbitmap,
> sparity->nsectors);
> --
> 2.12.1
>
>
>
If patch 4 and 5 are still supposed to fix the same problem, can you please
merge them into one patch so that a future bisect could be precise?
And while I believe this fixes the crash described in patch 4,
scrub_setup_recheck_block() also retrives all stripes, and if we scrub
one device, and another device is being replaced so it could be freed
during scrub, is it another potential race case?
Thanks,
-liubo
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