Commit 306eb6b4 authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
Browse files

nullb: support discard 



discard makes sense for memory backed disk. And also it's useful to test
if upper layer supports dicard correctly.

User configures 'discard' attribute to enable/disable dicard support.

Based on original patch from Kyungchan Koh

Signed-off-by: default avatarKyungchan Koh <kkc6196@fb.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 5bcd0e0c

drivers/block/null_blk.c

+41 −1
Original line number Diff line number Diff line
@@ -88,6 +88,7 @@ struct nullb_device { 
	bool use_per_node_hctx; /* use per-node allocation for hardware context */

	bool power; /* power on/off the device */

	bool memory_backed; /* if data is stored in memory */

	bool discard; /* if support discard */

};



struct nullb {
@@ -318,6 +319,7 @@ NULLB_DEVICE_ATTR(use_lightnvm, bool); 
NULLB_DEVICE_ATTR(blocking, bool);

NULLB_DEVICE_ATTR(use_per_node_hctx, bool);

NULLB_DEVICE_ATTR(memory_backed, bool);

NULLB_DEVICE_ATTR(discard, bool);



static ssize_t nullb_device_power_show(struct config_item *item, char *page)

{
@@ -373,6 +375,7 @@ static struct configfs_attribute *nullb_device_attrs[] = { 
	&nullb_device_attr_use_per_node_hctx,

	&nullb_device_attr_power,

	&nullb_device_attr_memory_backed,

	&nullb_device_attr_discard,

	NULL,

};
@@ -425,7 +428,7 @@ nullb_group_drop_item(struct config_group *group, struct config_item *item) 


static ssize_t memb_group_features_show(struct config_item *item, char *page)

{

	return snprintf(page, PAGE_SIZE, "memory_backed\n");

	return snprintf(page, PAGE_SIZE, "memory_backed,discard\n");

}



CONFIGFS_ATTR_RO(memb_group_, features);
@@ -815,6 +818,20 @@ next: 
	return 0;

}



static void null_handle_discard(struct nullb *nullb, sector_t sector, size_t n)

{

	size_t temp;



	spin_lock_irq(&nullb->lock);

	while (n > 0) {

		temp = min_t(size_t, n, nullb->dev->blocksize);

		null_free_sector(nullb, sector);

		sector += temp >> SECTOR_SHIFT;

		n -= temp;

	}

	spin_unlock_irq(&nullb->lock);

}



static int null_transfer(struct nullb *nullb, struct page *page,

	unsigned int len, unsigned int off, bool is_write, sector_t sector)

{
@@ -843,6 +860,11 @@ static int null_handle_rq(struct nullb_cmd *cmd) 


	sector = blk_rq_pos(rq);



	if (req_op(rq) == REQ_OP_DISCARD) {

		null_handle_discard(nullb, sector, blk_rq_bytes(rq));

		return 0;

	}



	spin_lock_irq(&nullb->lock);

	rq_for_each_segment(bvec, rq, iter) {

		len = bvec.bv_len;
@@ -871,6 +893,12 @@ static int null_handle_bio(struct nullb_cmd *cmd) 


	sector = bio->bi_iter.bi_sector;



	if (bio_op(bio) == REQ_OP_DISCARD) {

		null_handle_discard(nullb, sector,

			bio_sectors(bio) << SECTOR_SHIFT);

		return 0;

	}



	spin_lock_irq(&nullb->lock);

	bio_for_each_segment(bvec, bio, iter) {

		len = bvec.bv_len;
@@ -1207,6 +1235,16 @@ static void null_del_dev(struct nullb *nullb) 
	dev->nullb = NULL;

}



static void null_config_discard(struct nullb *nullb)

{

	if (nullb->dev->discard == false)

		return;

	nullb->q->limits.discard_granularity = nullb->dev->blocksize;

	nullb->q->limits.discard_alignment = nullb->dev->blocksize;

	blk_queue_max_discard_sectors(nullb->q, UINT_MAX >> 9);

	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, nullb->q);

}



static int null_open(struct block_device *bdev, fmode_t mode)

{

	return 0;
@@ -1448,6 +1486,8 @@ static int null_add_dev(struct nullb_device *dev) 
	blk_queue_logical_block_size(nullb->q, dev->blocksize);

	blk_queue_physical_block_size(nullb->q, dev->blocksize);



	null_config_discard(nullb);



	sprintf(nullb->disk_name, "nullb%d", nullb->index);



	if (dev->use_lightnvm)

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