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Re: [PATCH 1/3] Implement generic freeze feature

To: Takashi Sato <t-sato@xxxxxxxxxxxxx>
Subject: Re: [PATCH 1/3] Implement generic freeze feature
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Tue, 1 Jul 2008 04:08:44 -0400
Cc: akpm@xxxxxxxxxxxxxxxxxxxx, viro@xxxxxxxxxxxxxxxxxx, "linux-ext4@xxxxxxxxxxxxxxx" <linux-ext4@xxxxxxxxxxxxxxx>, "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>, "dm-devel@xxxxxxxxxx" <dm-devel@xxxxxxxxxx>, "linux-fsdevel@xxxxxxxxxxxxxxx" <linux-fsdevel@xxxxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, axboe@xxxxxxxxx, mtk.manpages@xxxxxxxxxxxxxx
In-reply-to: <20080630212323t-sato@xxxxxxxxxxxxxxx>
References: <20080630212323t-sato@xxxxxxxxxxxxxxx>
Sender: xfs-bounce@xxxxxxxxxxx
User-agent: Mutt/1.5.18 (2008-05-17)
>  {
>       struct super_block *sb;
>  
> +     if (test_and_set_bit(BD_FREEZE_OP, &bdev->bd_state))
> +             return ERR_PTR(-EBUSY);
> +
> +     sb = get_super(bdev);
> +
> +     /* If super_block has been already frozen, return. */
> +     if (sb && sb->s_frozen != SB_UNFROZEN) {
> +             drop_super(sb);
> +             clear_bit(BD_FREEZE_OP, &bdev->bd_state);
> +             return sb;
> +     }
> +
> +     if (sb)
> +             drop_super(sb);
> +
>       down(&bdev->bd_mount_sem);
>       sb = get_super(bdev);
>       if (sb && !(sb->s_flags & MS_RDONLY)) {
> @@ -219,6 +234,8 @@ struct super_block *freeze_bdev(struct b
>       }
>  
>       sync_blockdev(bdev);
> +     clear_bit(BD_FREEZE_OP, &bdev->bd_state);
> +

Please only clear BD_FREEZE_OP in thaw_bdev, that way you can also get
rid of the frozen check above, and the double-get_super.  Also
bd_mount_sem could be removed that way by checking for BD_FREEZE_OP
in the unmount path.

>  /*
> + * ioctl_freeze - Freeze the filesystem.
> + *
> + * @filp:    target file
> + *
> + * Call freeze_bdev() to freeze the filesystem.
> + */

This is not a kerneldoc comment.  But I think it can be simply removed
anyway, as it's a quite trivial function with static scope.

> +/*
> + * ioctl_thaw - Thaw the filesystem.
> + *
> + * @filp:    target file
> + *
> + * Call thaw_bdev() to thaw the filesystem.
> + */

Same here.


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