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authorChristoph Hellwig <hch@lst.de>2016-12-08 15:20:32 -0700
committerJens Axboe <axboe@fb.com>2016-12-09 08:30:51 -0700
commitf9d03f96b988002027d4b28ea1b7a24729a4c9b5 (patch)
treee4995a30bbe58290594e2ef29de5ae2785c6c9db /block
parentbe07e14f96e3121483339a64d917fddb3b86ba98 (diff)
downloadlinux-stericsson-f9d03f96b988002027d4b28ea1b7a24729a4c9b5.tar.gz
block: improve handling of the magic discard payload
Instead of allocating a single unused biovec for discard requests, send them down without any payload. Instead we allow the driver to add a "special" payload using a biovec embedded into struct request (unioned over other fields never used while in the driver), and overloading the number of segments for this case. This has a couple of advantages: - we don't have to allocate the bio_vec - the amount of special casing for discard requests in the block layer is significantly reduced - using this same scheme for other request types is trivial, which will be important for implementing the new WRITE_ZEROES op on devices where it actually requires a payload (e.g. SCSI) - we can get rid of playing games with the request length, as we'll never touch it and completions will work just fine - it will allow us to support ranged discard operations in the future by merging non-contiguous discard bios into a single request - last but not least it removes a lot of code This patch is the common base for my WIP series for ranges discards and to remove discard_zeroes_data in favor of always using REQ_OP_WRITE_ZEROES, so it would be good to get it in quickly. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block')
-rw-r--r--block/bio.c10
-rw-r--r--block/blk-core.c34
-rw-r--r--block/blk-lib.c2
-rw-r--r--block/blk-merge.c53
4 files changed, 21 insertions, 78 deletions
diff --git a/block/bio.c b/block/bio.c
index 83db1f37fd0b..2b375020fc49 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1840,15 +1840,7 @@ struct bio *bio_split(struct bio *bio, int sectors,
BUG_ON(sectors <= 0);
BUG_ON(sectors >= bio_sectors(bio));
- /*
- * Discards need a mutable bio_vec to accommodate the payload
- * required by the DSM TRIM and UNMAP commands.
- */
- if (bio_op(bio) == REQ_OP_DISCARD || bio_op(bio) == REQ_OP_SECURE_ERASE)
- split = bio_clone_bioset(bio, gfp, bs);
- else
- split = bio_clone_fast(bio, gfp, bs);
-
+ split = bio_clone_fast(bio, gfp, bs);
if (!split)
return NULL;
diff --git a/block/blk-core.c b/block/blk-core.c
index 4b7ec5958055..bd642a43b98b 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1475,38 +1475,6 @@ void blk_put_request(struct request *req)
}
EXPORT_SYMBOL(blk_put_request);
-/**
- * blk_add_request_payload - add a payload to a request
- * @rq: request to update
- * @page: page backing the payload
- * @offset: offset in page
- * @len: length of the payload.
- *
- * This allows to later add a payload to an already submitted request by
- * a block driver. The driver needs to take care of freeing the payload
- * itself.
- *
- * Note that this is a quite horrible hack and nothing but handling of
- * discard requests should ever use it.
- */
-void blk_add_request_payload(struct request *rq, struct page *page,
- int offset, unsigned int len)
-{
- struct bio *bio = rq->bio;
-
- bio->bi_io_vec->bv_page = page;
- bio->bi_io_vec->bv_offset = offset;
- bio->bi_io_vec->bv_len = len;
-
- bio->bi_iter.bi_size = len;
- bio->bi_vcnt = 1;
- bio->bi_phys_segments = 1;
-
- rq->__data_len = rq->resid_len = len;
- rq->nr_phys_segments = 1;
-}
-EXPORT_SYMBOL_GPL(blk_add_request_payload);
-
bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
struct bio *bio)
{
@@ -2642,6 +2610,8 @@ bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
return false;
}
+ WARN_ON_ONCE(req->rq_flags & RQF_SPECIAL_PAYLOAD);
+
req->__data_len -= total_bytes;
/* update sector only for requests with clear definition of sector */
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 510a6fb15318..ed89c8f4b2a0 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -80,7 +80,7 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
req_sects = end_sect - sector;
}
- bio = next_bio(bio, 1, gfp_mask);
+ bio = next_bio(bio, 0, gfp_mask);
bio->bi_iter.bi_sector = sector;
bio->bi_bdev = bdev;
bio_set_op_attrs(bio, op, 0);
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 1002afdfee99..182398cb1524 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -241,18 +241,13 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
if (!bio)
return 0;
- /*
- * This should probably be returning 0, but blk_add_request_payload()
- * (Christoph!!!!)
- */
switch (bio_op(bio)) {
case REQ_OP_DISCARD:
case REQ_OP_SECURE_ERASE:
- case REQ_OP_WRITE_SAME:
case REQ_OP_WRITE_ZEROES:
+ return 0;
+ case REQ_OP_WRITE_SAME:
return 1;
- default:
- break;
}
fbio = bio;
@@ -410,39 +405,21 @@ new_segment:
*bvprv = *bvec;
}
+static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,
+ struct scatterlist *sglist, struct scatterlist **sg)
+{
+ *sg = sglist;
+ sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
+ return 1;
+}
+
static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
struct scatterlist *sglist,
struct scatterlist **sg)
{
struct bio_vec bvec, bvprv = { NULL };
struct bvec_iter iter;
- int nsegs, cluster;
-
- nsegs = 0;
- cluster = blk_queue_cluster(q);
-
- switch (bio_op(bio)) {
- case REQ_OP_DISCARD:
- case REQ_OP_SECURE_ERASE:
- case REQ_OP_WRITE_ZEROES:
- /*
- * This is a hack - drivers should be neither modifying the
- * biovec, nor relying on bi_vcnt - but because of
- * blk_add_request_payload(), a discard bio may or may not have
- * a payload we need to set up here (thank you Christoph) and
- * bi_vcnt is really the only way of telling if we need to.
- */
- if (!bio->bi_vcnt)
- return 0;
- /* Fall through */
- case REQ_OP_WRITE_SAME:
- *sg = sglist;
- bvec = bio_iovec(bio);
- sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
- return 1;
- default:
- break;
- }
+ int cluster = blk_queue_cluster(q), nsegs = 0;
for_each_bio(bio)
bio_for_each_segment(bvec, bio, iter)
@@ -462,7 +439,11 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
struct scatterlist *sg = NULL;
int nsegs = 0;
- if (rq->bio)
+ if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
+ nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg);
+ else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
+ nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg);
+ else if (rq->bio)
nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
@@ -495,7 +476,7 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
* Something must have been wrong if the figured number of
* segment is bigger than number of req's physical segments
*/
- WARN_ON(nsegs > rq->nr_phys_segments);
+ WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
return nsegs;
}