[PATCH 1/7] block: add support for carrying a stream ID in a bio

Jens Axboe
2015-03-25T15:08:05Z

The top bits of bio->bi_flags are reserved for keeping the
allocation pool, set aside the next eight bits for carrying
a stream ID. That leaves us with support for 255 streams,
0 is reserved as a "stream not set" value.

Add helpers for setting/getting stream ID of a bio.

Signed-off-by: Jens Axboe <axboe@fb.com>
---
block/bio.c | 2 ++
block/blk-core.c | 3 +++
include/linux/blk_types.h | 28 +++++++++++++++++++++++++++-
3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index f66a4eae16ee..1cd3d745047c 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -567,6 +567,7 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
bio->bi_rw = bio_src->bi_rw;
bio->bi_iter = bio_src->bi_iter;
bio->bi_io_vec = bio_src->bi_io_vec;
+ bio_set_streamid(bio, bio_get_streamid(bio_src));
}
EXPORT_SYMBOL(__bio_clone_fast);

@@ -672,6 +673,7 @@ integrity_clone:
}
}

+ bio_set_streamid(bio, bio_get_streamid(bio_src));
return bio;
}
EXPORT_SYMBOL(bio_clone_bioset);
diff --git a/block/blk-core.c b/block/blk-core.c
index 794c3e7f01cf..6b7b8c95c4c3 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1928,6 +1928,9 @@ void generic_make_request(struct bio *bio)
do {
struct request_queue *q = bdev_get_queue(bio->bi_bdev);

+ if (bio_streamid_valid(bio))
+ blk_add_trace_msg(q, "StreamID=%u", bio_get_streamid(bio));
+
q->make_request_fn(q, bio);

bio = bio_list_pop(current->bio_list);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index c294e3e25e37..d6909007a3fe 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -138,9 +138,35 @@ struct bio {
#define BIO_POOL_BITS (4)
#define BIO_POOL_NONE ((1UL << BIO_POOL_BITS) - 1)
#define BIO_POOL_OFFSET (BITS_PER_LONG - BIO_POOL_BITS)
-#define BIO_POOL_MASK (1UL << BIO_POOL_OFFSET)
#define BIO_POOL_IDX(bio) ((bio)->bi_flags >> BIO_POOL_OFFSET)

+/*
+ * after the pool bits, next 8 bits are for the stream id
+ */
+#define BIO_STREAM_BITS (8)
+#define BIO_STREAM_OFFSET (BITS_PER_LONG - 12)
+#define BIO_STREAM_MASK ((1 << BIO_STREAM_BITS) - 1)
+
+static inline unsigned long streamid_to_flags(unsigned int id)
+{
+ return (unsigned long) (id & BIO_STREAM_MASK) << BIO_STREAM_OFFSET;
+}
+
+static inline void bio_set_streamid(struct bio *bio, unsigned int id)
+{
+ bio->bi_flags |= streamid_to_flags(id);
+}
+
+static inline unsigned int bio_get_streamid(struct bio *bio)
+{
+ return (bio->bi_flags >> BIO_STREAM_OFFSET) & BIO_STREAM_MASK;
+}
+
+static inline bool bio_streamid_valid(struct bio *bio)
+{
+ return bio_get_streamid(bio) != 0;
+}
+
#endif /* CONFIG_BLOCK */

/*
--
1.9.1