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st.ko: fix enlarge_buffer

PATCH Kai Mäkisara (Kolumbus) 1 participant 1 message Dec 16, 2013 1 message not in the archive SCSI

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Kai Mäkisara (Kolumbus)

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Quoted 7 lines · Bodo Stroesser

From: Bodo Stroesser <[email protected]>
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.

Quoted 9 lines

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 ;-)

Quoted 1 line
Cc Kai Makisara <[email protected]>
Acked-by Kai Mäkisara <[email protected]>

Thanks,
Kai

Quoted 16 lines
Signed-off-by Bodo Stroesser <[email protected]>

---

drivers/scsi/st.c +1 -1
@@ -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)

drivers/scsi/st.c static int enlarge_buffer(struct st_buff · line 3734

Quoted 9 lines
drivers/scsi/st.c +0 -3
@@ -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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