From: Jens Axboe <axboe@kernel.dk>
Date: Tue, 27 Jun 2017 15:22:02 +0000 (-0600)
Subject: block: add support for write hints in a bio
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=cb6934f8ea1a595902ca37e250e0917d4dd7b2a7;p=openwrt%2Fstaging%2Fblogic.git

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/block/bio.c b/block/bio.c
index 89a51bd49ab7..9cf98b29588a 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -596,6 +596,7 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
 	bio->bi_bdev = bio_src->bi_bdev;
 	bio_set_flag(bio, BIO_CLONED);
 	bio->bi_opf = bio_src->bi_opf;
+	bio->bi_write_hint = bio_src->bi_write_hint;
 	bio->bi_iter = bio_src->bi_iter;
 	bio->bi_io_vec = bio_src->bi_io_vec;
 
@@ -679,6 +680,7 @@ struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
 		return NULL;
 	bio->bi_bdev		= bio_src->bi_bdev;
 	bio->bi_opf		= bio_src->bi_opf;
+	bio->bi_write_hint	= bio_src->bi_write_hint;
 	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
 	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
 
diff --git a/block/blk-core.c b/block/blk-core.c
index 3c18ea60cb1c..af393d5a9680 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1765,6 +1765,7 @@ void blk_init_request_from_bio(struct request *req, struct bio *bio)
 		req->ioprio = ioc->ioprio;
 	else
 		req->ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+	req->write_hint = bio->bi_write_hint;
 	blk_rq_bio_prep(req->q, req, bio);
 }
 EXPORT_SYMBOL_GPL(blk_init_request_from_bio);
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 5df13041b851..99038830fb42 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -672,6 +672,13 @@ static struct request *attempt_merge(struct request_queue *q,
 	    !blk_write_same_mergeable(req->bio, next->bio))
 		return NULL;
 
+	/*
+	 * Don't allow merge of different write hints, or for a hint with
+	 * non-hint IO.
+	 */
+	if (req->write_hint != next->write_hint)
+		return NULL;
+
 	/*
 	 * If we are allowed to merge, then append bio list
 	 * from next to rq and release next. merge_requests_fn
@@ -791,6 +798,13 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 	    !blk_write_same_mergeable(rq->bio, bio))
 		return false;
 
+	/*
+	 * Don't allow merge of different write hints, or for a hint with
+	 * non-hint IO.
+	 */
+	if (rq->write_hint != bio->bi_write_hint)
+		return false;
+
 	return true;
 }
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index e210da6d14b8..d2eb87c84d82 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 bf2157141d53..0eebd3bcfd85 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;