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.
Cc: Kai Makisara <kai.makisara@xxxxxxxxxxx>
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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