block: add support for write hints in a bio
No functional changes in this patch, we just use up some holes
in the bio and request structures to define a write hint that
we psas down the stack.
Ensure that we don't merge requests that have different life time
hints assigned to them, and that we inherit the write hint when
cloning a bio.
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index e210da6..d2eb87c 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -56,6 +56,7 @@ struct bio {
*/
unsigned short bi_flags; /* status, etc and bvec pool number */
unsigned short bi_ioprio;
+ unsigned short bi_write_hint;
struct bvec_iter bi_iter;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index bf21571..0eebd3b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -225,6 +225,8 @@ struct request {
unsigned int extra_len; /* length of alignment and padding */
+ unsigned short write_hint;
+
unsigned long deadline;
struct list_head timeout_list;