From: Christoph Hellwig <hch@lst.de>
To: rusty@rustcorp.com.au
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH] virtio-blk: fix minimum number of S/G elements
Date: Tue, 25 May 2010 14:17:54 +0200 [thread overview]
Message-ID: <20100525121754.GA8456@lst.de> (raw)
We need at least one S/G element to operate properly, as does the block
layer which increments it to one anyway. We hit this due to a qemu
bug which advertises a sg_elements of 0 under some circumstances.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Index: linux-2.6/drivers/block/virtio_blk.c
===================================================================
--- linux-2.6.orig/drivers/block/virtio_blk.c 2010-05-25 13:21:44.136254435 +0200
+++ linux-2.6/drivers/block/virtio_blk.c 2010-05-25 13:59:04.334005727 +0200
@@ -287,7 +287,7 @@ static int __devinit virtblk_probe(struc
struct request_queue *q;
int err;
u64 cap;
- u32 v, blk_size, sg_elems, opt_io_size;
+ u32 v, blk_size, sg_elems = 0, opt_io_size;
u16 min_io_size;
u8 physical_block_exp, alignment_offset;
@@ -298,7 +298,9 @@ static int __devinit virtblk_probe(struc
err = virtio_config_val(vdev, VIRTIO_BLK_F_SEG_MAX,
offsetof(struct virtio_blk_config, seg_max),
&sg_elems);
- if (err)
+
+ /* We need at least one SG element */
+ if (!sg_elems)
sg_elems = 1;
/* We need an extra sg elements at head and tail. */
next reply other threads:[~2010-05-25 12:18 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-25 12:17 Christoph Hellwig [this message]
2010-05-26 8:03 ` [PATCH] virtio-blk: fix minimum number of S/G elements Rusty Russell
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