On 2.12.2013, at 21.00, Bodo Stroesser <bstroesser@xxxxxxxxxxxxxx> wrote:
> From: Bodo Stroesser <bstroesser@xxxxxxxxxxxxxx>
> Date: Mon, 2 Dec 2013 18:52:10 +0100
> Subject: [PATCH 1/3] st.ko: fix enlarge_buffer
>
> This patch removes a bug in enlarge_buffer() that can make a
> read or write fail under special conditions.
>
> After changing TRY_DIRECT_IO to 0 and ST_MAX_SG to 32 in
> st_options.h, a program that writes a first block of 128k and
> than a second bigger block (e.g. 256k) fails. The second write
> returns errno EOVERFLOW, as enlarge_buffer() checks the sg list
> and detects that it already is full.
> As enlarge_buffer uses different page allocation orders
> depending on the size of the buffer needed, the check does not
> make sense.
>
Yes, it is not useful any more. It may have been necessary at some time but I am now not sure about that either ;-)
> Cc: Kai Makisara <kai.makisara@xxxxxxxxxxx>
Acked-by: Kai Mäkisara <kai.makisara@xxxxxxxxxxx>
Thanks,
Kai
> Signed-off-by: Bodo Stroesser <bstroesser@xxxxxxxxxxxxxx>
>
> ---
>
> --- a/drivers/scsi/st.c 2013-12-02 18:52:10.000000000 +0100
> +++ b/drivers/scsi/st.c 2013-12-02 18:52:10.000000000 +0100
> @@ -3719,7 +3719,7 @@ static struct st_buffer *new_tape_buffer
>
> static int enlarge_buffer(struct st_buffer * STbuffer, int new_size, int need_dma)
> {
> - int segs, nbr, max_segs, b_size, order, got;
> + int segs, max_segs, b_size, order, got;
> gfp_t priority;
>
> if (new_size <= STbuffer->buffer_size)
> @@ -3729,9 +3729,6 @@ static int enlarge_buffer(struct st_buff
> normalize_buffer(STbuffer); /* Avoid extra segment */
>
> max_segs = STbuffer->use_sg;
> - nbr = max_segs - STbuffer->frp_segs;
> - if (nbr <= 0)
> - return 0;
>
> priority = GFP_KERNEL | __GFP_NOWARN;
> if (need_dma)
--
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