Re: [PATCH v2 1/4] Btrfs: fix wrong send_in_progress accounting

[Wang Shilong <wangshilong1991@gmail.com>]

Hello David,

> On Tue, Jan 07, 2014 at 05:25:18PM +0800, Wang Shilong 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.
> 
> Of course, the sort(). I think your fix adds some complexity that's not
> necessary. Whether the clone_roots array is sorted is not important, we
> just have to process each root once.
> 
> send_root becomes a clone_root member, so the missing part is to account
> in the rollback counter:
> 
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -4937,6 +4937,7 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
>         * for possible clone sources.
>         */
>        sctx->clone_roots[sctx->clone_roots_cnt++].root = sctx->send_root;
> +       clone_sources_to_rollback++;

Not really, If we fail to come here, we still need decrease @send_root.
Please correct me if i miss something here.^_^

Thanks,
Wang
> 
>        /* We do a bsearch later */
>        sort(sctx->clone_roots, sctx->clone_roots_cnt,
> @@ -4961,7 +4962,6 @@ out:
>                btrfs_root_dec_send_in_progress(sctx->clone_roots[i].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);
> ---
> --
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