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Subject[patch 21/24] virtio_blk: dont bounce highmem requests
2.6.30-stable review patch.  If anyone has any objections, please let us know.

From: Christoph Hellwig <>

commit 4eff3cae9c9809720c636e64bc72f212258e0bd5 upstream

virtio_blk: don't bounce highmem requests

By default a block driver bounces highmem requests, but virtio-blk is
perfectly fine with any request that fit into it's 64 bit addressing scheme,
mapped in the kernel virtual space or not.

Besides improving performance on highmem systems this also makes the
reproducible oops in __bounce_end_io go away (but hiding the real cause).

Signed-off-by: Christoph Hellwig <>
Signed-off-by: Rusty Russell <>
Cc: Chuck Ebbert <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/block/virtio_blk.c | 3 +++
1 file changed, 3 insertions(+)

--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -308,6 +308,9 @@ static int virtblk_probe(struct virtio_d
blk_queue_max_segment_size(vblk->disk->queue, -1U);

+ /* No need to bounce any requests */
+ blk_queue_bounce_limit(vblk->disk->queue, BLK_BOUNCE_ANY);
/* Host can optionally specify the block size of the device */
err = virtio_config_val(vdev, VIRTIO_BLK_F_BLK_SIZE,
offsetof(struct virtio_blk_config, blk_size),

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