linux-kernel - Re: [PATCH] btrfs: fix disk-io.c/btrfs_read_dev_super with BTRFS_SUPER_MIRROR

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Date:	Mon, 10 Sep 2012 01:24:45 -0600
From:	cwillu <cwillu@...llu.com>
To:	Wang Sheng-Hui <shhuiw@...il.com>
Cc:	chris.mason@...ionio.com, linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] btrfs: fix disk-io.c/btrfs_read_dev_super with
 BTRFS_SUPER_MIRROR_MAX to control the loops

On Mon, Sep 10, 2012 at 12:38 AM, Wang Sheng-Hui <shhuiw@...il.com> wrote:
> To check the duplicated super blocks, use BTRFS_SUPER_MIRROR_MAX
> as the loops limit.
>
> Signed-off-by: Wang Sheng-Hui <shhuiw@...il.com>
> ---
>  fs/btrfs/disk-io.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 22e98e0..a431144 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -2723,7 +2723,7 @@ struct buffer_head *btrfs_read_dev_super(struct block_device *bdev)
>          * So, we need to add a special mount option to scan for
>          * later supers, using BTRFS_SUPER_MIRROR_MAX instead
>          */
> -       for (i = 0; i < 1; i++) {
> +       for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
>                 bytenr = btrfs_sb_offset(i);
>                 if (bytenr + 4096 >= i_size_read(bdev->bd_inode))
>                         break;
> --
> 1.7.1
>
> --
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Please fix the comment as well; if we check all the supers, then
mounting as btrfs _will_ succeed after a different (non-btrfs)
filesystem is created on the partition/device, pretty much
guaranteeing it will be corrupted.
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