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block: support large requests in blk_rq_map_user_iov 

This patch adds support for larger requests in blk_rq_map_user_iov by
allowing it to build multiple bios for a request.  This functionality
used to exist for the non-vectored blk_rq_map_user in the past, and
this patch reuses the existing functionality for it on the unmap side,
which stuck around.  Thanks to the iov_iter API supporting multiple
bios is fairly trivial, as we can just iterate the iov until we've
consumed the whole iov_iter.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Jeff Lien <Jeff.Lien@hgst.com>
Tested-by: Jeff Lien <Jeff.Lien@hgst.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig 2016-03-02 18:07:14 +01:00 committed by Jens Axboe
parent f21018427c
commit 4d6af73d9e
1 changed files with 61 additions and 30 deletions
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91
block/blk-map.c
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@ -57,6 +57,49 @@ static int __blk_rq_unmap_user(struct bio *bio)
return ret;
}
static int __blk_rq_map_user_iov(struct request *rq,
struct rq_map_data *map_data, struct iov_iter *iter,
gfp_t gfp_mask, bool copy)
{
struct request_queue *q = rq->q;
struct bio *bio, *orig_bio;
int ret;
if (copy)
bio = bio_copy_user_iov(q, map_data, iter, gfp_mask);
else
bio = bio_map_user_iov(q, iter, gfp_mask);
if (IS_ERR(bio))
return PTR_ERR(bio);
if (map_data && map_data->null_mapped)
bio_set_flag(bio, BIO_NULL_MAPPED);
iov_iter_advance(iter, bio->bi_iter.bi_size);
if (map_data)
map_data->offset += bio->bi_iter.bi_size;
orig_bio = bio;
blk_queue_bounce(q, &bio);
/*
* We link the bounce buffer in and could have to traverse it
* later so we have to get a ref to prevent it from being freed
*/
bio_get(bio);
ret = blk_rq_append_bio(q, rq, bio);
if (ret) {
bio_endio(bio);
__blk_rq_unmap_user(orig_bio);
bio_put(bio);
return ret;
}
return 0;
}
/**
* blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
* @q: request queue where request should be inserted
@ -82,10 +125,11 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
struct rq_map_data *map_data,
const struct iov_iter *iter, gfp_t gfp_mask)
{
struct bio *bio;
int unaligned = 0;
struct iov_iter i;
struct iovec iov, prv = {.iov_base = NULL, .iov_len = 0};
bool copy = (q->dma_pad_mask & iter->count) || map_data;
struct bio *bio = NULL;
struct iov_iter i;
int ret;
if (!iter || !iter->count)
return -EINVAL;
@ -101,42 +145,29 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
*/
if ((uaddr & queue_dma_alignment(q)) ||
iovec_gap_to_prv(q, &prv, &iov))
unaligned = 1;
copy = true;
prv.iov_base = iov.iov_base;
prv.iov_len = iov.iov_len;
}
if (unaligned || (q->dma_pad_mask & iter->count) || map_data)
bio = bio_copy_user_iov(q, map_data, iter, gfp_mask);
else
bio = bio_map_user_iov(q, iter, gfp_mask);
if (IS_ERR(bio))
return PTR_ERR(bio);
if (map_data && map_data->null_mapped)
bio_set_flag(bio, BIO_NULL_MAPPED);
if (bio->bi_iter.bi_size != iter->count) {
/*
* Grab an extra reference to this bio, as bio_unmap_user()
* expects to be able to drop it twice as it happens on the
* normal IO completion path
*/
bio_get(bio);
bio_endio(bio);
__blk_rq_unmap_user(bio);
return -EINVAL;
}
i = *iter;
do {
ret =__blk_rq_map_user_iov(rq, map_data, &i, gfp_mask, copy);
if (ret)
goto unmap_rq;
if (!bio)
bio = rq->bio;
} while (iov_iter_count(&i));
if (!bio_flagged(bio, BIO_USER_MAPPED))
rq->cmd_flags |= REQ_COPY_USER;
blk_queue_bounce(q, &bio);
bio_get(bio);
blk_rq_bio_prep(q, rq, bio);
return 0;
unmap_rq:
__blk_rq_unmap_user(bio);
rq->bio = NULL;
return -EINVAL;
}
EXPORT_SYMBOL(blk_rq_map_user_iov);