Impact: implement new API
There still are a few places where request is allocated statically and
manually initialized. Till now, those sites used their own custom
mechanisms to pass data buffer through request queue. This patch
implements blk_rq_map_kern_prealloc() which initializes rq with
pre-allocated bio and bvec so that those code paths can be converted
to bio.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
---
block/blk-map.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++
fs/bio.c | 23 ++++++++++++++++++++++
include/linux/bio.h | 3 ++
include/linux/blkdev.h | 4 +++
4 files changed, 80 insertions(+), 0 deletions(-)
diff --git a/block/blk-map.c b/block/blk-map.c
index f103729..c50aac2 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -317,3 +317,53 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
return 0;
}
EXPORT_SYMBOL(blk_rq_map_kern);
+
+/**
+ * blk_rq_map_kern_prealloc - map kernel data using preallocated structures
+ * @q: request queue where request should be inserted
+ * @rq: request to fill
+ * @bio: bio to use
+ * @bvec: bio_vec array to use
+ * @bvec_len: the number of available bvecs in @bvec
+ * @kbuf: the kernel buffer to map
+ * @len: length of @kbuf
+ * @force: bypass @kbuf alignment and on stack check
+ *
+ * Description:
+ * @len bytes at @kbuf will be mapped into @rq using @bio and
+ * @bvec. The buffer must be suitable for direct mapping and
+ * should not require more than @bvec_len elements to map. This
+ * function doesn't do any allocation and can be called from atomic
+ * context. 0 is returned on success, -errno on failure. Note
+ * that this function does not handle bouncing.
+ *
+ * WARNING: Using this function is strongly discouraged. Use
+ * blk_rq_map_kern() if at all possible.
+ */
+int blk_rq_map_kern_prealloc(struct request_queue *q,
+ struct request *rq, struct bio *bio,
+ struct bio_vec *bvec, unsigned short bvec_len,
+ void *kbuf, unsigned int len, bool force)
+{
+ int error;
+
+ if (len > (q->max_hw_sectors << 9))
+ return -EINVAL;
+ if (!len || !kbuf)
+ return -EINVAL;
+ if (!force &&
+ (!blk_rq_aligned(q, kbuf, len) || object_is_on_stack(kbuf)))
+ return -EINVAL;
+
+ error = bio_map_kern_prealloc(q, bio, bvec, bvec_len, kbuf, len);
+ if (error)
+ return error;
+
+ if (rq_data_dir(rq) == WRITE)
+ bio->bi_rw |= (1 << BIO_RW);
+
+ blk_rq_bio_prep(q, rq, bio);
+ rq->buffer = rq->data = NULL;
+ return 0;
+}
+EXPORT_SYMBOL(blk_rq_map_kern_prealloc);
diff --git a/fs/bio.c b/fs/bio.c
index 746b566..ab3c9c9 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1165,6 +1165,29 @@ struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
return bio;
}
+/**
+ * bio_map_kern_prealloc - map kernel address into preallocated bio/bvec
+ * @q: the struct request_queue for the bio
+ * @bio: bio to initialize
+ * @bvec: bio_vec array to initialize
+ * @bvec_len: how many elements are available in @bvec
+ * @data: pointer to buffer to map
+ * @len: length in bytes
+ *
+ * Map @data into @bvec and initialize @bio with it. If there
+ * aren't enough @bvec entries, -EINVAL is returned.
+ */
+int bio_map_kern_prealloc(struct request_queue *q, struct bio *bio,
+ struct bio_vec *bvec, unsigned short bvec_len,
+ void *data, unsigned int len)
+{
+ bio_init(bio);
+ bio->bi_io_vec = bvec;
+ bio->bi_max_vecs = bvec_len;
+
+ return __bio_map_kern(q, bio, data, len);
+}
+
static void bio_copy_kern_endio(struct bio *bio, int err)
{
struct bio_vec *bvec;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index d8bd43b..39619eb 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -388,6 +388,9 @@ extern struct bio *bio_map_user_iov(struct request_queue *,
extern void bio_unmap_user(struct bio *);
extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,
gfp_t);
+extern int bio_map_kern_prealloc(struct request_queue *q, struct bio *bio,
+ struct bio_vec *bvec, unsigned short bvec_len,
+ void *data, unsigned int len);
extern struct bio *bio_copy_kern(struct request_queue *, void *, unsigned int,
gfp_t, int);
extern void bio_set_pages_dirty(struct bio *bio);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 465d6ba..e322e94 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -781,6 +781,10 @@ extern int blk_rq_map_user(struct request_queue *, struct request *,
gfp_t);
extern int blk_rq_unmap_user(struct bio *);
extern int blk_rq_map_kern(struct request_queue *, struct request *, void *, unsigned int, gfp_t);
+extern int blk_rq_map_kern_prealloc(struct request_queue *q,
+ struct request *rq, struct bio *bio,
+ struct bio_vec *bvec, unsigned short bvec_len,
+ void *kbuf, unsigned int len, bool force);
extern int blk_rq_map_user_iov(struct request_queue *, struct request *,
struct rq_map_data *, struct sg_iovec *, int,
unsigned int, gfp_t);
--
1.6.0.2
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