On Thu, Jun 19, 2014 at 10:42:54AM +0800, Miao Xie wrote:
> The deadlock happened when we mount degraded filesystem, the reproduced
> steps are following:
> # mkfs.btrfs -f -m raid1 -d raid1 <dev0> <dev1>
> # echo 1 > /sys/block/`basename <dev0>`/device/delete
> # mount -o degraded <dev1> <mnt>
>
> The reason was that the counter -- bi_remaining was wrong. If the missing
> or unwriteable device was the last device in the mapping array, we would
> not submit the original bio, so we shouldn't increase bi_remaining of it
> in btrfs_end_bio(), or we would skip the final endio handle.
>
> Fix this problem by adding a flag into btrfs bio structure. If we submit
> the original bio, we will set the flag, and we increase bi_remaining counter,
> or we don't.
>
> Though there is another way to fix it -- decrease bi_remaining counter of the
> original bio when we make sure the original bio is not submitted, this method
> need add more check and is easy to make mistake.
Happen to look at this problem, looks good to me.
Reviewed-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
-liubo
>
> Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/volumes.c | 7 ++++++-
> fs/btrfs/volumes.h | 3 +++
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 31f9036..4ca3c92 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -5415,8 +5415,12 @@ static void btrfs_end_bio(struct bio *bio, int err)
> set_bit(BIO_UPTODATE, &bio->bi_flags);
> err = 0;
> }
> +
> + if (likely(bbio->flags & BTRFS_BIO_ORIG_BIO_SUBMITTED))
> + bio_endio_nodec(bio, err);
> + else
> + bio_endio(bio, err);
> kfree(bbio);
> - bio_endio_nodec(bio, err);
> } else if (!is_orig_bio) {
> bio_put(bio);
> }
> @@ -5671,6 +5675,7 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
> BUG_ON(!bio); /* -ENOMEM */
> } else {
> bio = first_bio;
> + bbio->flags |= BTRFS_BIO_ORIG_BIO_SUBMITTED;
> }
>
> submit_stripe_bio(root, bbio, bio,
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 1a15bbe..2aaa00c 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -190,11 +190,14 @@ struct btrfs_bio_stripe {
> struct btrfs_bio;
> typedef void (btrfs_bio_end_io_t) (struct btrfs_bio *bio, int err);
>
> +#define BTRFS_BIO_ORIG_BIO_SUBMITTED 0x1
> +
> struct btrfs_bio {
> atomic_t stripes_pending;
> struct btrfs_fs_info *fs_info;
> bio_end_io_t *end_io;
> struct bio *orig_bio;
> + unsigned long flags;
> void *private;
> atomic_t error;
> int max_errors;
> --
> 1.9.3
>
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