[PATCH 1/2] block: document BLK_STS_AGAIN usage

[Hannes Reinecke <hare@suse.de>]

BLK_STS_AGAIN should only be used if RQF_NOWAIT is set and the bio
would block. So we'd better document that to avoid accidental misuse.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 include/linux/blk_types.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 1973ef9bd40f..8fb8f79cb74e 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -105,6 +105,10 @@ typedef u16 blk_short_t;
 /* hack for device mapper, don't use elsewhere: */
 #define BLK_STS_DM_REQUEUE    ((__force blk_status_t)11)
 
+/*
+ * BLK_STS_AGAIN should only be returned if RQF_NOWAIT is set
+ * and the bio would block (cf bio_wouldblock_error())
+ */
 #define BLK_STS_AGAIN		((__force blk_status_t)12)
 
 /*
-- 
2.29.2