Commit c15227de authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: use normal I/O path for discard requests 



prepare_discard_fn() was being called in a place where memory allocation
was effectively impossible.  This makes it inappropriate for all but
the most trivial translations of Linux's DISCARD operation to the block
command set.  Additionally adding a payload there makes the ownership
of the bio backing unclear as it's now allocated by the device driver
and not the submitter as usual.

It is replaced with QUEUE_FLAG_DISCARD which is used to indicate whether
the queue supports discard operations or not.  blkdev_issue_discard now
allocates a one-page, sector-length payload which is the right thing
for the common ATA and SCSI implementations.

The mtd implementation of prepare_discard_fn() is replaced with simply
checking for the request being a discard.

Largely based on a previous patch from Matthew Wilcox <matthew@wil.cx>
which did the prepare_discard_fn but not the different payload allocation
yet.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 3bd0f0c7

block/blk-barrier.c

+30 −5
Original line number Diff line number Diff line
@@ -350,6 +350,7 @@ static void blkdev_discard_end_io(struct bio *bio, int err) 


	if (bio->bi_private)

		complete(bio->bi_private);

	__free_page(bio_page(bio));



	bio_put(bio);

}
@@ -372,26 +373,44 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
	struct request_queue *q = bdev_get_queue(bdev);

	int type = flags & DISCARD_FL_BARRIER ?

		DISCARD_BARRIER : DISCARD_NOBARRIER;

	struct bio *bio;

	struct page *page;

	int ret = 0;



	if (!q)

		return -ENXIO;



	if (!q->prepare_discard_fn)

	if (!blk_queue_discard(q))

		return -EOPNOTSUPP;



	while (nr_sects && !ret) {

		struct bio *bio = bio_alloc(gfp_mask, 0);

		if (!bio)

			return -ENOMEM;

		unsigned int sector_size = q->limits.logical_block_size;



		bio = bio_alloc(gfp_mask, 1);

		if (!bio)

			goto out;

		bio->bi_sector = sector;

		bio->bi_end_io = blkdev_discard_end_io;

		bio->bi_bdev = bdev;

		if (flags & DISCARD_FL_WAIT)

			bio->bi_private = &wait;



		bio->bi_sector = sector;

		/*

		 * Add a zeroed one-sector payload as that's what

		 * our current implementations need.  If we'll ever need

		 * more the interface will need revisiting.

		 */

		page = alloc_page(GFP_KERNEL | __GFP_ZERO);

		if (!page)

			goto out_free_bio;

		if (bio_add_pc_page(q, bio, page, sector_size, 0) < sector_size)

			goto out_free_page;



		/*

		 * And override the bio size - the way discard works we

		 * touch many more blocks on disk than the actual payload

		 * length.

		 */

		if (nr_sects > queue_max_hw_sectors(q)) {

			bio->bi_size = queue_max_hw_sectors(q) << 9;

			nr_sects -= queue_max_hw_sectors(q);
@@ -414,5 +433,11 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
		bio_put(bio);

	}

	return ret;

out_free_page:

	__free_page(page);

out_free_bio:

	bio_put(bio);

out:

	return -ENOMEM;

}

EXPORT_SYMBOL(blkdev_issue_discard);

block/blk-core.c

+1 −2
Original line number Diff line number Diff line
@@ -1124,7 +1124,6 @@ void init_request_from_bio(struct request *req, struct bio *bio) 
		req->cmd_flags |= REQ_DISCARD;

		if (bio_rw_flagged(bio, BIO_RW_BARRIER))

			req->cmd_flags |= REQ_SOFTBARRIER;

		req->q->prepare_discard_fn(req->q, req);

	} else if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER)))

		req->cmd_flags |= REQ_HARDBARRIER;
@@ -1470,7 +1469,7 @@ static inline void __generic_make_request(struct bio *bio) 
			goto end_io;



		if (bio_rw_flagged(bio, BIO_RW_DISCARD) &&

		    !q->prepare_discard_fn) {

		    !blk_queue_discard(q)) {

			err = -EOPNOTSUPP;

			goto end_io;

		}

block/blk-settings.c

+0 −17
Original line number Diff line number Diff line
@@ -33,23 +33,6 @@ void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn) 
}

EXPORT_SYMBOL(blk_queue_prep_rq);



/**

 * blk_queue_set_discard - set a discard_sectors function for queue

 * @q:		queue

 * @dfn:	prepare_discard function

 *

 * It's possible for a queue to register a discard callback which is used

 * to transform a discard request into the appropriate type for the

 * hardware. If none is registered, then discard requests are failed

 * with %EOPNOTSUPP.

 *

 */

void blk_queue_set_discard(struct request_queue *q, prepare_discard_fn *dfn)

{

	q->prepare_discard_fn = dfn;

}

EXPORT_SYMBOL(blk_queue_set_discard);



/**

 * blk_queue_merge_bvec - set a merge_bvec function for queue

 * @q:		queue

drivers/mtd/mtd_blkdevs.c

+5 −14
Original line number Diff line number Diff line
@@ -32,14 +32,6 @@ struct mtd_blkcore_priv { 
	spinlock_t queue_lock;

};



static int blktrans_discard_request(struct request_queue *q,

				    struct request *req)

{

	req->cmd_type = REQ_TYPE_LINUX_BLOCK;

	req->cmd[0] = REQ_LB_OP_DISCARD;

	return 0;

}



static int do_blktrans_request(struct mtd_blktrans_ops *tr,

			       struct mtd_blktrans_dev *dev,

			       struct request *req)
@@ -52,10 +44,6 @@ static int do_blktrans_request(struct mtd_blktrans_ops *tr, 


	buf = req->buffer;



	if (req->cmd_type == REQ_TYPE_LINUX_BLOCK &&

	    req->cmd[0] == REQ_LB_OP_DISCARD)

		return tr->discard(dev, block, nsect);



	if (!blk_fs_request(req))

		return -EIO;
@@ -63,6 +51,9 @@ static int do_blktrans_request(struct mtd_blktrans_ops *tr, 
	    get_capacity(req->rq_disk))

		return -EIO;



	if (blk_discard_rq(req))

		return tr->discard(dev, block, nsect);



	switch(rq_data_dir(req)) {

	case READ:

		for (; nsect > 0; nsect--, block++, buf += tr->blksize)
@@ -380,8 +371,8 @@ int register_mtd_blktrans(struct mtd_blktrans_ops *tr) 
	tr->blkcore_priv->rq->queuedata = tr;

	blk_queue_logical_block_size(tr->blkcore_priv->rq, tr->blksize);

	if (tr->discard)

		blk_queue_set_discard(tr->blkcore_priv->rq,

				      blktrans_discard_request);

		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,

					tr->blkcore_priv->rq);



	tr->blkshift = ffs(tr->blksize) - 1;

drivers/staging/dst/dcore.c

+1 −1
Original line number Diff line number Diff line
@@ -102,7 +102,7 @@ static int dst_request(struct request_queue *q, struct bio *bio) 
	struct dst_node *n = q->queuedata;

	int err = -EIO;



	if (bio_empty_barrier(bio) && !q->prepare_discard_fn) {

	if (bio_empty_barrier(bio) && !blk_queue_discard(q)) {

		/*

		 * This is a dirty^Wnice hack, but if we complete this

		 * operation with -EOPNOTSUPP like intended, XFS

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