Commit c66fd019 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: make the block holder code optional 



Move the block holder code into a separate file as it is not in any way
related to the other block_dev.c code, and add a new selectable config
option for it so that we don't have to build it without any remapped
drivers selected.

The Kconfig symbol contains a _DEPRECATED suffix to match the comments
added in commit 49731baa
("block: restore multiple bd_link_disk_holder() support").

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarMike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20210804094147.459763-2-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 2112f5c1

block/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -241,4 +241,8 @@ config BLK_MQ_RDMA 
config BLK_PM

	def_bool BLOCK && PM



# do not use in new code

config BLOCK_HOLDER_DEPRECATED

	bool



source "block/Kconfig.iosched"

block/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -41,3 +41,4 @@ obj-$(CONFIG_BLK_SED_OPAL) += sed-opal.o 
obj-$(CONFIG_BLK_PM)		+= blk-pm.o

obj-$(CONFIG_BLK_INLINE_ENCRYPTION)	+= keyslot-manager.o blk-crypto.o

obj-$(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK)	+= blk-crypto-fallback.o

obj-$(CONFIG_BLOCK_HOLDER_DEPRECATED)	+= holder.o

block/holder.c

0 → 100644
+139 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only

#include <linux/genhd.h>



struct bd_holder_disk {

	struct list_head	list;

	struct gendisk		*disk;

	int			refcnt;

};



static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,

						  struct gendisk *disk)

{

	struct bd_holder_disk *holder;



	list_for_each_entry(holder, &bdev->bd_holder_disks, list)

		if (holder->disk == disk)

			return holder;

	return NULL;

}



static int add_symlink(struct kobject *from, struct kobject *to)

{

	return sysfs_create_link(from, to, kobject_name(to));

}



static void del_symlink(struct kobject *from, struct kobject *to)

{

	sysfs_remove_link(from, kobject_name(to));

}



/**

 * bd_link_disk_holder - create symlinks between holding disk and slave bdev

 * @bdev: the claimed slave bdev

 * @disk: the holding disk

 *

 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.

 *

 * This functions creates the following sysfs symlinks.

 *

 * - from "slaves" directory of the holder @disk to the claimed @bdev

 * - from "holders" directory of the @bdev to the holder @disk

 *

 * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is

 * passed to bd_link_disk_holder(), then:

 *

 *   /sys/block/dm-0/slaves/sda --> /sys/block/sda

 *   /sys/block/sda/holders/dm-0 --> /sys/block/dm-0

 *

 * The caller must have claimed @bdev before calling this function and

 * ensure that both @bdev and @disk are valid during the creation and

 * lifetime of these symlinks.

 *

 * CONTEXT:

 * Might sleep.

 *

 * RETURNS:

 * 0 on success, -errno on failure.

 */

int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)

{

	struct bd_holder_disk *holder;

	int ret = 0;



	mutex_lock(&bdev->bd_disk->open_mutex);



	WARN_ON_ONCE(!bdev->bd_holder);



	/* FIXME: remove the following once add_disk() handles errors */

	if (WARN_ON(!disk->slave_dir || !bdev->bd_holder_dir))

		goto out_unlock;



	holder = bd_find_holder_disk(bdev, disk);

	if (holder) {

		holder->refcnt++;

		goto out_unlock;

	}



	holder = kzalloc(sizeof(*holder), GFP_KERNEL);

	if (!holder) {

		ret = -ENOMEM;

		goto out_unlock;

	}



	INIT_LIST_HEAD(&holder->list);

	holder->disk = disk;

	holder->refcnt = 1;



	ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));

	if (ret)

		goto out_free;



	ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);

	if (ret)

		goto out_del;

	/*

	 * bdev could be deleted beneath us which would implicitly destroy

	 * the holder directory.  Hold on to it.

	 */

	kobject_get(bdev->bd_holder_dir);



	list_add(&holder->list, &bdev->bd_holder_disks);

	goto out_unlock;



out_del:

	del_symlink(disk->slave_dir, bdev_kobj(bdev));

out_free:

	kfree(holder);

out_unlock:

	mutex_unlock(&bdev->bd_disk->open_mutex);

	return ret;

}

EXPORT_SYMBOL_GPL(bd_link_disk_holder);



/**

 * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()

 * @bdev: the calimed slave bdev

 * @disk: the holding disk

 *

 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.

 *

 * CONTEXT:

 * Might sleep.

 */

void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)

{

	struct bd_holder_disk *holder;



	mutex_lock(&bdev->bd_disk->open_mutex);

	holder = bd_find_holder_disk(bdev, disk);

	if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {

		del_symlink(disk->slave_dir, bdev_kobj(bdev));

		del_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);

		kobject_put(bdev->bd_holder_dir);

		list_del_init(&holder->list);

		kfree(holder);

	}

	mutex_unlock(&bdev->bd_disk->open_mutex);

}

EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);

drivers/md/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ if MD 


config BLK_DEV_MD

	tristate "RAID support"

	select BLOCK_HOLDER_DEPRECATED if SYSFS

	help

	  This driver lets you combine several hard disk partitions into one

	  logical block device. This can be used to simply append one
@@ -201,6 +202,7 @@ config BLK_DEV_DM_BUILTIN 


config BLK_DEV_DM

	tristate "Device mapper support"

	select BLOCK_HOLDER_DEPRECATED if SYSFS

	select BLK_DEV_DM_BUILTIN

	depends on DAX || DAX=n

	help

drivers/md/bcache/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 


config BCACHE

	tristate "Block device as cache"

	select BLOCK_HOLDER_DEPRECATED if SYSFS

	select CRC64

	help

	Allows a block device to be used as cache for other devices; uses