On Sat, Jan 18, 2014 at 4:58 AM, Wang Shilong
<wangsl.f...@cn.fujitsu.com> wrote:
> Steps to reproduce:
>  # mkfs.btrfs -f /dev/sda8
>  # mount /dev/sda8 /mnt
>  # btrfs sub snapshot -r /mnt /mnt/snap1
>  # btrfs sub snapshot -r /mnt /mnt/snap2
>  # btrfs send /mnt/snap1 -p /mnt/snap2 -f /mnt/1
>  # dmesg
>
> The problem is that we will sort clone roots(include @send_root), it
> might push @send_root before thus @send_root's @send_in_progress will
> be decreased twice.
>
> Cc: David Sterba <dste...@suse.cz>
> Signed-off-by: Wang Shilong <wangsl.f...@cn.fujitsu.com>
> ---
> changelog
> v2->v3:
>         add comments as david addressed.
> v1->v2:
>         use right root to check
> ---
>  fs/btrfs/send.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
> index bff0b1a..83b6bdb 100644
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -4752,6 +4752,7 @@ long btrfs_ioctl_send(struct file *mnt_file, void 
> __user *arg_)
>         u32 i;
>         u64 *clone_sources_tmp = NULL;
>         int clone_sources_to_rollback = 0;
> +       int sort_clone_roots = 0;
>
>         if (!capable(CAP_SYS_ADMIN))
>                 return -EPERM;
> @@ -4942,6 +4943,7 @@ long btrfs_ioctl_send(struct file *mnt_file, void 
> __user *arg_)
>         sort(sctx->clone_roots, sctx->clone_roots_cnt,
>                         sizeof(*sctx->clone_roots), __clone_root_cmp_sort,
>                         NULL);
> +       sort_clone_roots = 1;
>
>         ret = send_subvol(sctx);
>         if (ret < 0)
> @@ -4957,11 +4959,22 @@ long btrfs_ioctl_send(struct file *mnt_file, void 
> __user *arg_)
>         }
>
>  out:
> -       for (i = 0; sctx && i < clone_sources_to_rollback; i++)
> -               btrfs_root_dec_send_in_progress(sctx->clone_roots[i].root);
> +       if (sort_clone_roots) {
> +               for (i = 0; i < sctx->clone_roots_cnt; i++)
> +                       btrfs_root_dec_send_in_progress(
> +                                       sctx->clone_roots[i].root);

sctx can be NULL here, anywhere after the 'out' label.

> +       } else {
> +               for (i = 0; sctx && i < clone_sources_to_rollback; i++)
> +                       btrfs_root_dec_send_in_progress(
> +                                       sctx->clone_roots[i].root);

Same here.

> +               /*
> +                * if we fail to add @send_root in clone roots, we still
> +                * need to decrease @send_in_progress count here.
> +                */
> +               btrfs_root_dec_send_in_progress(send_root);
> +       }
>         if (sctx && !IS_ERR_OR_NULL(sctx->parent_root))
>                 btrfs_root_dec_send_in_progress(sctx->parent_root);
> -       btrfs_root_dec_send_in_progress(send_root);
>
>         kfree(arg);
>         vfree(clone_sources_tmp);
> --
> 1.8.3.1
>
> --
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-- 
Filipe David Manana,

"Reasonable men adapt themselves to the world.
 Unreasonable men adapt the world to themselves.
 That's why all progress depends on unreasonable men."
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