[PATCH] md: improve raid10 "IO Barrier" concept

raid10 needs to put up a barrier to new requests while it does resync or other
background recovery.  The code for this is currently open-coded, slighty
obscure by its use of two waitqueues, and not documented.

This patch gathers all the related code into 4 functions, and includes a
comment which (hopefully) explains what is happening.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/raid/raid10.h b/include/linux/raid/raid10.h
index 60708789c8f9..08317b77802b 100644
--- a/include/linux/raid/raid10.h
+++ b/include/linux/raid/raid10.h
@@ -39,11 +39,11 @@ struct r10_private_data_s {
 
         spinlock_t              resync_lock;
         int nr_pending;
+        int nr_waiting;
         int barrier;
         sector_t                next_resync;
 
-        wait_queue_head_t       wait_idle;
-        wait_queue_head_t       wait_resume;
+        wait_queue_head_t       wait_barrier;
 
         mempool_t *r10bio_pool;
         mempool_t *r10buf_pool;