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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 49731ba ("block: restore multiple bd_link_disk_holder() support"). Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Mike Snitzer <snitzer@redhat.com> Link: https://lore.kernel.org/r/20210804094147.459763-2-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,139 @@ | ||
| // 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); |
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