[SCSI] Convert SCSI mid-layer to scsi_execute_async

Add scsi helpers to create really-large-requests and convert
scsi-ml to scsi_execute_async().

Per Jens's previous comments, I placed this function in scsi_lib.c.
I made it follow all the queue's limits - I think I did at least :), so
I removed the warning on the function header.

I think the scsi_execute_* functions should eventually take a request_queue
and be placed some place where the dm-multipath hw_handler can use them
if that failover code is going to stay in the kernel. That conversion
patch will be sent in another mail though.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/fs/bio.c b/fs/bio.c
index 460554b07ff9..4d21ee3873ec 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -386,6 +386,25 @@ static int __bio_add_page(request_queue_t *q, struct bio *bio, struct page
 }
 
 /**
+ *	bio_add_pc_page	-	attempt to add page to bio
+ *	@bio: destination bio
+ *	@page: page to add
+ *	@len: vec entry length
+ *	@offset: vec entry offset
+ *
+ *	Attempt to add a page to the bio_vec maplist. This can fail for a
+ *	number of reasons, such as the bio being full or target block
+ *	device limitations. The target block device must allow bio's
+ *      smaller than PAGE_SIZE, so it is always possible to add a single
+ *      page to an empty bio. This should only be used by REQ_PC bios.
+ */
+int bio_add_pc_page(request_queue_t *q, struct bio *bio, struct page *page,
+		    unsigned int len, unsigned int offset)
+{
+	return __bio_add_page(q, bio, page, len, offset);
+}
+
+/**
  *	bio_add_page	-	attempt to add page to bio
  *	@bio: destination bio
  *	@page: page to add
@@ -1228,6 +1247,7 @@ EXPORT_SYMBOL(bio_clone);
 EXPORT_SYMBOL(bio_phys_segments);
 EXPORT_SYMBOL(bio_hw_segments);
 EXPORT_SYMBOL(bio_add_page);
+EXPORT_SYMBOL(bio_add_pc_page);
 EXPORT_SYMBOL(bio_get_nr_vecs);
 EXPORT_SYMBOL(bio_map_user);
 EXPORT_SYMBOL(bio_unmap_user);