[PATCH RFC 05/16] block: Add REQ_ATOMIC flag

[John Garry]

From: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>

Add flag REQ_ATOMIC, meaning an atomic operation. This should only be
used in conjunction with REQ_OP_WRITE.

We will not add a special "request atomic write" operation, as to try to
avoid maintenance effort for an operation which is almost the same as
REQ_OP_WRITE.

This flag was originally proposed by Chris Mason for an atomic writes
proposal some time ago.

Signed-off-by: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>
Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
---
 include/linux/blk_types.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 99be590f952f..347b52e00322 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -417,6 +417,7 @@ enum req_flag_bits {
 	__REQ_SWAP,		/* swap I/O */
 	__REQ_DRV,		/* for driver use */
 
+	__REQ_ATOMIC,		/* for atomic write operations */
 	/*
 	 * Command specific flags, keep last:
 	 */
@@ -444,6 +445,7 @@ enum req_flag_bits {
 #define REQ_BACKGROUND	(__force blk_opf_t)(1ULL << __REQ_BACKGROUND)
 #define REQ_NOWAIT	(__force blk_opf_t)(1ULL << __REQ_NOWAIT)
 #define REQ_CGROUP_PUNT	(__force blk_opf_t)(1ULL << __REQ_CGROUP_PUNT)
+#define REQ_ATOMIC	(__force blk_opf_t)(1ULL << __REQ_ATOMIC)
 
 #define REQ_NOUNMAP	(__force blk_opf_t)(1ULL << __REQ_NOUNMAP)
 #define REQ_POLLED	(__force blk_opf_t)(1ULL << __REQ_POLLED)
-- 
2.31.1