On Tue, Apr 16, 2013 at 05:20:28PM +0800, Liu Bo wrote:
> We need such a sanity check for wrong start when we defrag a file, otherwise,
> even with a wrong start that's larger than file size, we can end up changing
> not only inode's force compress flag but also FS's incompat flags.

The range->start check is good, but why are you worried about the
incompat flag? LZO support has been around for more than 2 years.

> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -1152,8 +1152,11 @@ int btrfs_defrag_file(struct inode *inode, struct file 
> *file,
>       u64 new_align = ~((u64)128 * 1024 - 1);
>       struct page **pages = NULL;
>  
> -     if (extent_thresh == 0)
> -             extent_thresh = 256 * 1024;
> +     if (isize == 0)
> +             return 0;
> +
> +     if (range->start >= isize)
> +             return -EINVAL;
...
> -     if (isize == 0)
> -             return 0;
> +     if (extent_thresh == 0)
> +             extent_thresh = 256 * 1024;

That's a more logical order of the checks, good.

Reviewed-by: David Sterba <dste...@suse.cz>
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