md/raid10: simplify the splitting of requests.

raid10 splits requests in two different ways for two different
reasons.

First, bio_split() is used to ensure the bio fits with a chunk.
Second, multiple r10bio structures are allocated to represent the
different sections that need to go to different devices, to avoid
known bad blocks.

This can be simplified to just use bio_split() once, and not to use
multiple r10bios.
We delay the split until we know a maximum bio size that can
be handled with a single r10bio, and then split the bio and queue
the remainder for later handling.

As with raid1, we allocate a new bio_set to help with the splitting.
It is not correct to use fs_bio_set in a device driver.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h
index 3162615e57bd..735ce1a3d260 100644
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -82,6 +82,7 @@ struct r10conf {
 	mempool_t		*r10bio_pool;
 	mempool_t		*r10buf_pool;
 	struct page		*tmppage;
+	struct bio_set		*bio_split;
 
 	/* When taking over an array from a different personality, we store
 	 * the new thread here until we fully activate the array.