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Message-ID: <20100525121754.GA8456@lst.de> Date: Tue, 25 May 2010 14:17:54 +0200 From: Christoph Hellwig <hch@....de> To: rusty@...tcorp.com.au Cc: linux-kernel@...r.kernel.org Subject: [PATCH] virtio-blk: fix minimum number of S/G elements 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@....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. */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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