New block API:
given a struct bio allocates a new request. This is the parallel of
generic_make_request for BLOCK_PC commands users.
The passed bio may be a chained-bio. The bio is bounced if needed
inside the call to this member.
This is in the effort of un-exporting blk_rq_append_bio().
Signed-off-by: Boaz Harrosh <bharrosh@xxxxxxxxxxx>
CC: Jeff Garzik <jeff@xxxxxxxxxx>
---
block/blk-core.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/blkdev.h | 2 +
2 files changed, 56 insertions(+), 0 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index a2d97de..3145a37 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -891,6 +891,60 @@ struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
EXPORT_SYMBOL(blk_get_request);
/**
+ * blk_make_request - given a bio, allocate a corresponding struct request.
+ *
+ * @bio: The bio describing the memory mappings that will be submitted for IO.
+ * It may be a chained-bio properly constructed by block/bio layer.
+ *
+ * blk_make_request is the parallel of generic_make_request for BLOCK_PC
+ * type commands. Where the struct request needs to be farther initialized by
+ * the caller. It is passed a &struct bio, which describes the memory info of
+ * the I/O transfer.
+ *
+ * The caller of blk_make_request must make sure that bi_io_vec
+ * are set to describe the memory buffers. That bio_data_dir() will return
+ * the needed direction of the request. (And all bio's in the passed bio-chain
+ * are properly set accordingly)
+ *
+ * If called under none-sleepable conditions, mapped bio buffers must not
+ * need bouncing, by calling the appropriate masked or flagged allocator,
+ * suitable for the target device. Otherwise the call to blk_queue_bounce will
+ * BUG.
+ *
+ * WARNING: When allocating/cloning a bio-chain, careful consideration should be
+ * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
+ * anything but the first bio in the chain. Otherwise you risk waiting for IO
+ * completion of a bio that hasn't been submitted yet, thus resulting in a
+ * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
+ * of bio_alloc(), as that avoids the mempool deadlock.
+ * If possible a big IO should be split into smaller parts when allocation
+ * fails. Partial allocation should not be an error, or you risk a live-lock.
+ */
+struct request *blk_make_request(struct request_queue *q, struct bio *bio,
+ gfp_t gfp_mask)
+{
+ struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
+
+ if (unlikely(!rq))
+ return ERR_PTR(-ENOMEM);
+
+ for_each_bio(bio) {
+ struct bio *bounce_bio = bio;
+ int ret;
+
+ blk_queue_bounce(q, &bounce_bio);
+ ret = blk_rq_append_bio(q, rq, bounce_bio);
+ if (unlikely(ret)) {
+ blk_put_request(rq);
+ return ERR_PTR(ret);
+ }
+ }
+
+ return rq;
+}
+EXPORT_SYMBOL(blk_make_request);
+
+/**
* blk_requeue_request - put a request back on queue
* @q: request queue where request should be inserted
* @rq: request to be inserted
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f9d60a7..88a83e1 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -740,6 +740,8 @@ extern void blk_rq_init(struct request_queue *q, struct request *rq);
extern void blk_put_request(struct request *);
extern void __blk_put_request(struct request_queue *, struct request *);
extern struct request *blk_get_request(struct request_queue *, int, gfp_t);
+extern struct request *blk_make_request(struct request_queue *, struct bio *,
+ gfp_t);
extern void blk_insert_request(struct request_queue *, struct request *, int, void *);
extern void blk_requeue_request(struct request_queue *, struct request *);
extern int blk_rq_check_limits(struct request_queue *q, struct request *rq);
--
1.6.2.1
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