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Re: [PATCH] bufio: fix the next_buf calculation
From: |
Daniel Kiper |
Subject: |
Re: [PATCH] bufio: fix the next_buf calculation |
Date: |
Tue, 17 Apr 2018 19:11:34 +0200 |
User-agent: |
Mutt/1.3.28i |
CC-ing Vladimir.
On Mon, Apr 16, 2018 at 06:05:04PM +0800, Michael Chang wrote:
> The next_buf is the offset to the next cached block rounded to the size of
> bufio->block_size. However the calculation needs the block_size to be in power
> of 2 is not always valid. As an example, files with smaller size than
> block_size will have the block_size leveled to the size of file which can be
> set arbitrary value.
>
> This patch fixes the next_buf calculation to accept any integers.
>
> Signed-off-by: Michael Chang <address@hidden>
> ---
> grub-core/io/bufio.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/grub-core/io/bufio.c b/grub-core/io/bufio.c
> index 22438277d..d0b0f71b6 100644
> --- a/grub-core/io/bufio.c
> +++ b/grub-core/io/bufio.c
> @@ -132,7 +132,7 @@ grub_bufio_read (grub_file_t file, char *buf, grub_size_t
> len)
> return res;
>
> /* Need to read some more. */
> - next_buf = (file->offset + res + len - 1) & ~((grub_off_t)
> bufio->block_size - 1);
> + next_buf = (grub_divmod64 (file->offset + res + len - 1,
> bufio->block_size, NULL)) * bufio->block_size;
Should not you fix this in grub_bufio_open()? I think that
you should look for closest power of 2 in it.
Daniel