---
 block/ll_rw_blk.c   |   79 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/bio.c            |    3 +
 fs/buffer.c         |    3 +
 include/linux/bio.h |    1 
 4 files changed, 86 insertions(+)

Index: linux-2.6/block/ll_rw_blk.c
===================================================================
--- linux-2.6.orig/block/ll_rw_blk.c	2007-09-30 22:48:37.000000000 -0700
+++ linux-2.6/block/ll_rw_blk.c	2007-09-30 23:09:24.000000000 -0700
@@ -2923,6 +2923,78 @@ static void init_request_from_bio(struct
 	req->start_time = jiffies;
 }
 
+
+static void blk_queue_de_virtualize(struct request_queue *q,
+					struct bio **bio_orig)
+{
+	struct page *page;
+	struct bio *bio = NULL;
+	int i, nr;
+	struct bio_vec *to, *from;
+	int segments;
+
+	if (!(bio->bi_flags & BIO_VIRTUAL_COMPOUND))
+		return;
+
+	/* Calculate number of segments. */
+	segments = 0;
+	bio_for_each_segment(from, *bio_orig, i) {
+		page = from->bv_page;
+
+		if (!PageVcompound(page))
+			segments++;
+
+		segments += page_cache_pages(page);
+	}
+	if (seg == (*bio_orig)->bi_vcnt)
+		/* No need for any new pages */
+		return;
+
+	/* Linearize the pages */
+
+	bio = bio_alloc(GFP_NOIO, segments);
+
+	nr = 0;
+	bio_for_each_segment(from, *bio_orig, i) {
+		page = from->bv_page;
+
+		if (!PageVcompound(page)) {
+			/* Straight copy is possible */
+			to = bio->bi_io_vec + nr++;
+			to->bv_page = from->bv_page;
+			to->bv_len = from->bv->len;
+			to->bv_offset = from->bv_offset;
+			continue;
+		}
+
+		address = compound_address(page);
+		pages = page_cache_pages(page);
+		offset = from->bv_offset;
+		length = from->bv_len;
+
+		for (i = offset >> PAGE_SHIFT; i < pages; i++)
+			to = bio->bi_io_vec + nr++;
+			to->bv_page = page_cache_nth(page, i);
+			to->bv_len = min(PAGE_SIZE, length);
+			to->bv_offset = offset;
+			offset = 0;
+			length -= PAGE_SIZE
+		}
+	}
+
+	bio->bi_bdev = (*bio_orig)->bi_bdev;
+        bio->bi_sector = (*bio_orig)->bi_sector;
+        bio->bi_rw = (*bio_orig)->bi_rw;
+
+        bio->bi_vcnt = nr;
+        bio->bi_idx = (*bio_orig)->bi_idx;
+        bio->bi_size = (*bio_orig)->bi_size;
+
+	bio_put(*bio_orig);
+        *bio_orig = bio;
+}
+
+
 static int __make_request(struct request_queue *q, struct bio *bio)
 {
 	struct request *req;
@@ -2934,6 +3006,13 @@ static int __make_request(struct request
 	nr_sectors = bio_sectors(bio);
 
 	/*
+	 * If there are any virtual compounds on the bio then those must
+	 * now be separated out into individual pages since there is
+	 * no guarantee for physical linearity.
+	 */
+	blk_queue_de_virtualize(q, &bio);
+
+	/*
 	 * low level driver can indicate that it wants pages above a
 	 * certain limit bounced to low memory (ie for highmem, or even
 	 * ISA dma in theory)
Index: linux-2.6/fs/bio.c
===================================================================
--- linux-2.6.orig/fs/bio.c	2007-09-30 22:40:22.000000000 -0700
+++ linux-2.6/fs/bio.c	2007-09-30 22:45:48.000000000 -0700
@@ -328,6 +328,9 @@ static int __bio_add_page(struct request
 	if (unlikely(bio_flagged(bio, BIO_CLONED)))
 		return 0;
 
+	if (PageHead(page) && compound_pagearray(page))
+		bio->bi_flags |= BIO_VIRTUAL_COMPOUND;
+
 	if (((bio->bi_size + len) >> 9) > max_sectors)
 		return 0;
 
Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c	2007-09-30 22:46:17.000000000 -0700
+++ linux-2.6/fs/buffer.c	2007-09-30 22:47:05.000000000 -0700
@@ -2689,6 +2689,9 @@ int submit_bh(int rw, struct buffer_head
 	bio->bi_end_io = end_bio_bh_io_sync;
 	bio->bi_private = bh;
 
+	if (PageVcompound(bh->bh_bpage))
+		bio->bi_flags |= BIO_VIRTUAL_COMPOUND;
+
 	bio_get(bio);
 	submit_bio(rw, bio);
 
Index: linux-2.6/include/linux/bio.h
===================================================================
--- linux-2.6.orig/include/linux/bio.h	2007-09-30 22:39:58.000000000 -0700
+++ linux-2.6/include/linux/bio.h	2007-09-30 22:40:18.000000000 -0700
@@ -127,6 +127,7 @@ struct bio {
 #define BIO_BOUNCED	5	/* bio is a bounce bio */
 #define BIO_USER_MAPPED 6	/* contains user pages */
 #define BIO_EOPNOTSUPP	7	/* not supported */
+#define BIO_VMALLOC	8	/* Bio has vmalloc'ed memory */
 #define bio_flagged(bio, flag)	((bio)->bi_flags & (1 << (flag)))
 
 /*