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Date: Wed, 25 Mar 2009 17:18:35 +0200
From: Boaz Harrosh <bharrosh@...asas.com>
To: Tejun Heo <tj@...nel.org>
CC: bzolnier@...il.com, linux-kernel@...r.kernel.org, axboe@...nel.dk,
linux-ide@...r.kernel.org
Subject: Re: [PATCH 03/14] block: implement blk_rq_map_kern_prealloc()
Tejun Heo wrote:
> 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@...nel.org>
> Cc: Jens Axboe <axboe@...nel.dk>
Hi dear Tejun Heo
I have a similar, totally unrelated patch queued, perhaps we can unify
the efforts, to satisfy both our needs in one stone.
I've sent this patch:
http://www.spinics.net/lists/linux-scsi/msg34082.html
In an effort to un-export blk_rq_append_bio().
Perhaps you could reorder the code below a bit?
My proposal is:
* blk_rq_map_kern_prealloc => is simplified to be
int blk_rq_map_bio(struct request_queue *q, struct request *rq,
struct bio *bio);
* The extra checks currently inside blk_rq_map_kern_prealloc are moved
to bio_map_kern_prealloc()
* Users call bio_map_kern_prealloc() directly and then use blk_rq_map_bio()
in a two stage process.
So blk_rq_map_bio becomes a BLOCK_PC command's way of a pre-allocated bio
the way FS_PC commands use generic_make_request.
Thanks for doing all this. BTW' how close are we to remove req->data and req->buffer
Have a good day
Boaz
> ---
> 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);
--
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