diff --git a/block/blktrace.c b/block/blktrace.c
index 9b4da4ae3c7d..568588cd16b2 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -235,7 +235,7 @@ static void blk_trace_cleanup(struct blk_trace *bt)
 	kfree(bt);
 }
 
-static int blk_trace_remove(struct request_queue *q)
+int blk_trace_remove(struct request_queue *q)
 {
 	struct blk_trace *bt;
 
@@ -249,6 +249,7 @@ static int blk_trace_remove(struct request_queue *q)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(blk_trace_remove);
 
 static int blk_dropped_open(struct inode *inode, struct file *filp)
 {
@@ -316,18 +317,17 @@ static struct rchan_callbacks blk_relay_callbacks = {
 /*
  * Setup everything required to start tracing
  */
-int do_blk_trace_setup(struct request_queue *q, struct block_device *bdev,
+int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 			struct blk_user_trace_setup *buts)
 {
 	struct blk_trace *old_bt, *bt = NULL;
 	struct dentry *dir = NULL;
-	char b[BDEVNAME_SIZE];
 	int ret, i;
 
 	if (!buts->buf_size || !buts->buf_nr)
 		return -EINVAL;
 
-	strcpy(buts->name, bdevname(bdev, b));
+	strcpy(buts->name, name);
 
 	/*
 	 * some device names have larger paths - convert the slashes
@@ -352,7 +352,7 @@ int do_blk_trace_setup(struct request_queue *q, struct block_device *bdev,
 		goto err;
 
 	bt->dir = dir;
-	bt->dev = bdev->bd_dev;
+	bt->dev = dev;
 	atomic_set(&bt->dropped, 0);
 
 	ret = -EIO;
@@ -399,8 +399,8 @@ int do_blk_trace_setup(struct request_queue *q, struct block_device *bdev,
 	return ret;
 }
 
-static int blk_trace_setup(struct request_queue *q, struct block_device *bdev,
-			   char __user *arg)
+int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
+		    char __user *arg)
 {
 	struct blk_user_trace_setup buts;
 	int ret;
@@ -409,7 +409,7 @@ static int blk_trace_setup(struct request_queue *q, struct block_device *bdev,
 	if (ret)
 		return -EFAULT;
 
-	ret = do_blk_trace_setup(q, bdev, &buts);
+	ret = do_blk_trace_setup(q, name, dev, &buts);
 	if (ret)
 		return ret;
 
@@ -418,8 +418,9 @@ static int blk_trace_setup(struct request_queue *q, struct block_device *bdev,
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(blk_trace_setup);
 
-static int blk_trace_startstop(struct request_queue *q, int start)
+int blk_trace_startstop(struct request_queue *q, int start)
 {
 	struct blk_trace *bt;
 	int ret;
@@ -452,6 +453,7 @@ static int blk_trace_startstop(struct request_queue *q, int start)
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(blk_trace_startstop);
 
 /**
  * blk_trace_ioctl: - handle the ioctls associated with tracing
@@ -464,6 +466,7 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
 {
 	struct request_queue *q;
 	int ret, start = 0;
+	char b[BDEVNAME_SIZE];
 
 	q = bdev_get_queue(bdev);
 	if (!q)
@@ -473,7 +476,8 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
 
 	switch (cmd) {
 	case BLKTRACESETUP:
-		ret = blk_trace_setup(q, bdev, arg);
+		strcpy(b, bdevname(bdev, b));
+		ret = blk_trace_setup(q, b, bdev->bd_dev, arg);
 		break;
 	case BLKTRACESTART:
 		start = 1;
diff --git a/block/compat_ioctl.c b/block/compat_ioctl.c
index cae0a852619e..b73373216b0e 100644
--- a/block/compat_ioctl.c
+++ b/block/compat_ioctl.c
@@ -545,6 +545,7 @@ static int compat_blk_trace_setup(struct block_device *bdev, char __user *arg)
 	struct blk_user_trace_setup buts;
 	struct compat_blk_user_trace_setup cbuts;
 	struct request_queue *q;
+	char b[BDEVNAME_SIZE];
 	int ret;
 
 	q = bdev_get_queue(bdev);
@@ -554,6 +555,8 @@ static int compat_blk_trace_setup(struct block_device *bdev, char __user *arg)
 	if (copy_from_user(&cbuts, arg, sizeof(cbuts)))
 		return -EFAULT;
 
+	strcpy(b, bdevname(bdev, b));
+
 	buts = (struct blk_user_trace_setup) {
 		.act_mask = cbuts.act_mask,
 		.buf_size = cbuts.buf_size,
@@ -565,7 +568,7 @@ static int compat_blk_trace_setup(struct block_device *bdev, char __user *arg)
 	memcpy(&buts.name, &cbuts.name, 32);
 
 	mutex_lock(&bdev->bd_mutex);
-	ret = do_blk_trace_setup(q, bdev, &buts);
+	ret = do_blk_trace_setup(q, b, bdev->bd_dev, &buts);
 	mutex_unlock(&bdev->bd_mutex);
 	if (ret)
 		return ret;
diff --git a/block/elevator.c b/block/elevator.c
index f9736fbdab03..8cd5775acd7a 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -741,7 +741,21 @@ struct request *elv_next_request(struct request_queue *q)
 			q->boundary_rq = NULL;
 		}
 
-		if ((rq->cmd_flags & REQ_DONTPREP) || !q->prep_rq_fn)
+		if (rq->cmd_flags & REQ_DONTPREP)
+			break;
+
+		if (q->dma_drain_size && rq->data_len) {
+			/*
+			 * make sure space for the drain appears we
+			 * know we can do this because max_hw_segments
+			 * has been adjusted to be one fewer than the
+			 * device can handle
+			 */
+			rq->nr_phys_segments++;
+			rq->nr_hw_segments++;
+		}
+
+		if (!q->prep_rq_fn)
 			break;
 
 		ret = q->prep_rq_fn(q, rq);
@@ -754,6 +768,16 @@ struct request *elv_next_request(struct request_queue *q)
 			 * avoid resource deadlock.  REQ_STARTED will
 			 * prevent other fs requests from passing this one.
 			 */
+			if (q->dma_drain_size && rq->data_len &&
+			    !(rq->cmd_flags & REQ_DONTPREP)) {
+				/*
+				 * remove the space for the drain we added
+				 * so that we don't add it again
+				 */
+				--rq->nr_phys_segments;
+				--rq->nr_hw_segments;
+			}
+
 			rq = NULL;
 			break;
 		} else if (ret == BLKPREP_KILL) {
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index c16fdfed8c62..1932a56f5e4b 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -720,6 +720,45 @@ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
 
 EXPORT_SYMBOL(blk_queue_stack_limits);
 
+/**
+ * blk_queue_dma_drain - Set up a drain buffer for excess dma.
+ *
+ * @q:  the request queue for the device
+ * @buf:	physically contiguous buffer
+ * @size:	size of the buffer in bytes
+ *
+ * Some devices have excess DMA problems and can't simply discard (or
+ * zero fill) the unwanted piece of the transfer.  They have to have a
+ * real area of memory to transfer it into.  The use case for this is
+ * ATAPI devices in DMA mode.  If the packet command causes a transfer
+ * bigger than the transfer size some HBAs will lock up if there
+ * aren't DMA elements to contain the excess transfer.  What this API
+ * does is adjust the queue so that the buf is always appended
+ * silently to the scatterlist.
+ *
+ * Note: This routine adjusts max_hw_segments to make room for
+ * appending the drain buffer.  If you call
+ * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
+ * calling this routine, you must set the limit to one fewer than your
+ * device can support otherwise there won't be room for the drain
+ * buffer.
+ */
+int blk_queue_dma_drain(struct request_queue *q, void *buf,
+				unsigned int size)
+{
+	if (q->max_hw_segments < 2 || q->max_phys_segments < 2)
+		return -EINVAL;
+	/* make room for appending the drain */
+	--q->max_hw_segments;
+	--q->max_phys_segments;
+	q->dma_drain_buffer = buf;
+	q->dma_drain_size = size;
+
+	return 0;
+}
+
+EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
+
 /**
  * blk_queue_segment_boundary - set boundary rules for segment merging
  * @q:  the request queue for the device
@@ -1374,6 +1413,16 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 		bvprv = bvec;
 	} /* segments in rq */
 
+	if (q->dma_drain_size) {
+		sg->page_link &= ~0x02;
+		sg = sg_next(sg);
+		sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
+			    q->dma_drain_size,
+			    ((unsigned long)q->dma_drain_buffer) &
+			    (PAGE_SIZE - 1));
+		nsegs++;
+	}
+
 	if (sg)
 		sg_mark_end(sg);
 
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 17216b76efdc..aba28f335b88 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -48,6 +48,7 @@ static int sg_version_num = 30534;	/* 2 digits for each component */
 #include <linux/blkdev.h>
 #include <linux/delay.h>
 #include <linux/scatterlist.h>
+#include <linux/blktrace_api.h>
 
 #include "scsi.h"
 #include <scsi/scsi_dbg.h>
@@ -1067,6 +1068,17 @@ sg_ioctl(struct inode *inode, struct file *filp,
 	case BLKSECTGET:
 		return put_user(sdp->device->request_queue->max_sectors * 512,
 				ip);
+	case BLKTRACESETUP:
+		return blk_trace_setup(sdp->device->request_queue,
+				       sdp->disk->disk_name,
+				       sdp->device->sdev_gendev.devt,
+				       (char *)arg);
+	case BLKTRACESTART:
+		return blk_trace_startstop(sdp->device->request_queue, 1);
+	case BLKTRACESTOP:
+		return blk_trace_startstop(sdp->device->request_queue, 0);
+	case BLKTRACETEARDOWN:
+		return blk_trace_remove(sdp->device->request_queue);
 	default:
 		if (read_only)
 			return -EPERM;	/* don't know so take safe approach */
diff --git a/fs/bio.c b/fs/bio.c
index d59ddbf79626..242e409dab4b 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -248,11 +248,13 @@ inline int bio_hw_segments(struct request_queue *q, struct bio *bio)
  */
 void __bio_clone(struct bio *bio, struct bio *bio_src)
 {
-	struct request_queue *q = bdev_get_queue(bio_src->bi_bdev);
-
 	memcpy(bio->bi_io_vec, bio_src->bi_io_vec,
 		bio_src->bi_max_vecs * sizeof(struct bio_vec));
 
+	/*
+	 * most users will be overriding ->bi_bdev with a new target,
+	 * so we don't set nor calculate new physical/hw segment counts here
+	 */
 	bio->bi_sector = bio_src->bi_sector;
 	bio->bi_bdev = bio_src->bi_bdev;
 	bio->bi_flags |= 1 << BIO_CLONED;
@@ -260,8 +262,6 @@ void __bio_clone(struct bio *bio, struct bio *bio_src)
 	bio->bi_vcnt = bio_src->bi_vcnt;
 	bio->bi_size = bio_src->bi_size;
 	bio->bi_idx = bio_src->bi_idx;
-	bio_phys_segments(q, bio);
-	bio_hw_segments(q, bio);
 }
 
 /**
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index b71c3900810d..71e7a847dffc 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -356,6 +356,8 @@ struct request_queue
 	unsigned int		max_segment_size;
 
 	unsigned long		seg_boundary_mask;
+	void			*dma_drain_buffer;
+	unsigned int		dma_drain_size;
 	unsigned int		dma_alignment;
 
 	struct blk_queue_tag	*queue_tags;
@@ -692,6 +694,8 @@ extern void blk_queue_max_hw_segments(struct request_queue *, unsigned short);
 extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
 extern void blk_queue_hardsect_size(struct request_queue *, unsigned short);
 extern void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b);
+extern int blk_queue_dma_drain(struct request_queue *q, void *buf,
+			       unsigned int size);
 extern void blk_queue_segment_boundary(struct request_queue *, unsigned long);
 extern void blk_queue_prep_rq(struct request_queue *, prep_rq_fn *pfn);
 extern void blk_queue_merge_bvec(struct request_queue *, merge_bvec_fn *);
@@ -768,12 +772,7 @@ static inline int bdev_hardsect_size(struct block_device *bdev)
 
 static inline int queue_dma_alignment(struct request_queue *q)
 {
-	int retval = 511;
-
-	if (q && q->dma_alignment)
-		retval = q->dma_alignment;
-
-	return retval;
+	return q ? q->dma_alignment : 511;
 }
 
 /* assumes size > 256 */
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index 7e11d23ac36a..06dadba349ac 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -148,7 +148,7 @@ extern int blk_trace_ioctl(struct block_device *, unsigned, char __user *);
 extern void blk_trace_shutdown(struct request_queue *);
 extern void __blk_add_trace(struct blk_trace *, sector_t, int, int, u32, int, int, void *);
 extern int do_blk_trace_setup(struct request_queue *q,
-	struct block_device *bdev, struct blk_user_trace_setup *buts);
+	char *name, dev_t dev, struct blk_user_trace_setup *buts);
 
 
 /**
@@ -282,6 +282,11 @@ static inline void blk_add_trace_remap(struct request_queue *q, struct bio *bio,
 	__blk_add_trace(bt, from, bio->bi_size, bio->bi_rw, BLK_TA_REMAP, !bio_flagged(bio, BIO_UPTODATE), sizeof(r), &r);
 }
 
+extern int blk_trace_setup(request_queue_t *q, char *name, dev_t dev,
+			   char __user *arg);
+extern int blk_trace_startstop(request_queue_t *q, int start);
+extern int blk_trace_remove(request_queue_t *q);
+
 #else /* !CONFIG_BLK_DEV_IO_TRACE */
 #define blk_trace_ioctl(bdev, cmd, arg)		(-ENOTTY)
 #define blk_trace_shutdown(q)			do { } while (0)
@@ -290,7 +295,10 @@ static inline void blk_add_trace_remap(struct request_queue *q, struct bio *bio,
 #define blk_add_trace_generic(q, rq, rw, what)	do { } while (0)
 #define blk_add_trace_pdu_int(q, what, bio, pdu)	do { } while (0)
 #define blk_add_trace_remap(q, bio, dev, f, t)	do {} while (0)
-#define do_blk_trace_setup(q, bdev, buts)	(-ENOTTY)
+#define do_blk_trace_setup(q, name, dev, buts)	(-ENOTTY)
+#define blk_trace_setup(q, name, dev, arg)	(-ENOTTY)
+#define blk_trace_startstop(q, start)		(-ENOTTY)
+#define blk_trace_remove(q)			(-ENOTTY)
 #endif /* CONFIG_BLK_DEV_IO_TRACE */
 #endif /* __KERNEL__ */
 #endif