On Fri, Oct 13, 2017 at 09:42:18PM +0800, Anand Jain wrote:
> When one of the device is missing, bbio_error() takes care
> of setting the error status. And if its only IO that is
> pending in that stripe, it fails to check the status of the
> other IO at %bbio_error before setting the error %bi_status
> for the %orig_bio. Fix this by checking if %bbio->error is
> has crossed the %bbio->max_errors. Thxs.
>
> Reproducer as below fdatasync error is seen intermittently.
>
> mount -o degraded /dev/sdc /btrfs
> dd status=none if=/dev/zero of=$(mktemp /btrfs/XXX) bs=4096 count=1 conv=fdatasync
>
> dd: fdatasync failed for ‘/btrfs/LSe’: Input/output error
>
> The reason for the intermittences of the problem is because..
> following condition has to be met, which depends on timely
> coordination.
> In btrfs_map_bio()
> . The RAID1 the missing device has to be at %dev_nr = 1
> In bbio_error()
> . Before bbio_error() is called the bio of the not-missing
> device at %dev_nr=0 must be completed so that the below
> condition is true
> if (atomic_dec_and_test(&bbio->stripes_pending)) {
>
> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
> ---
> fs/btrfs/volumes.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 9af633dcf015..efd502176915 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -6131,7 +6131,10 @@ static void bbio_error(struct btrfs_bio *bbio, struct bio *bio, u64 logical)
>
> btrfs_io_bio(bio)->mirror_num = bbio->mirror_num;
> bio->bi_iter.bi_sector = logical >> 9;
> - bio->bi_status = BLK_STS_IOERR;
> + if (atomic_read(&bbio->error) > bbio->max_errors)
> + bio->bi_status = BLK_STS_IOERR;
> + else
> + bio->bi_status = 0;
Thanks for the fix, I'd prefer BLK_STS_OK rather than 0.
With that,
Reviewed-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
-liubo
> btrfs_end_bbio(bbio, bio);
> }
> }
> --
> 2.13.1
>
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