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1// SPDX-License-Identifier: GPL-2.0-only2#include <linux/blkdev.h>3#include <linux/slab.h>4 5struct bd_holder_disk {6 struct list_head list;7 struct kobject *holder_dir;8 int refcnt;9};10 11static DEFINE_MUTEX(blk_holder_mutex);12 13static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,14 struct gendisk *disk)15{16 struct bd_holder_disk *holder;17 18 list_for_each_entry(holder, &disk->slave_bdevs, list)19 if (holder->holder_dir == bdev->bd_holder_dir)20 return holder;21 return NULL;22}23 24static int add_symlink(struct kobject *from, struct kobject *to)25{26 return sysfs_create_link(from, to, kobject_name(to));27}28 29static void del_symlink(struct kobject *from, struct kobject *to)30{31 sysfs_remove_link(from, kobject_name(to));32}33 34/**35 * bd_link_disk_holder - create symlinks between holding disk and slave bdev36 * @bdev: the claimed slave bdev37 * @disk: the holding disk38 *39 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.40 *41 * This functions creates the following sysfs symlinks.42 *43 * - from "slaves" directory of the holder @disk to the claimed @bdev44 * - from "holders" directory of the @bdev to the holder @disk45 *46 * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is47 * passed to bd_link_disk_holder(), then:48 *49 * /sys/block/dm-0/slaves/sda --> /sys/block/sda50 * /sys/block/sda/holders/dm-0 --> /sys/block/dm-051 *52 * The caller must have claimed @bdev before calling this function and53 * ensure that both @bdev and @disk are valid during the creation and54 * lifetime of these symlinks.55 *56 * CONTEXT:57 * Might sleep.58 *59 * RETURNS:60 * 0 on success, -errno on failure.61 */62int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)63{64 struct bd_holder_disk *holder;65 int ret = 0;66 67 if (WARN_ON_ONCE(!disk->slave_dir))68 return -EINVAL;69 70 if (bdev->bd_disk == disk)71 return -EINVAL;72 73 /*74 * del_gendisk drops the initial reference to bd_holder_dir, so we75 * need to keep our own here to allow for cleanup past that point.76 */77 mutex_lock(&bdev->bd_disk->open_mutex);78 if (!disk_live(bdev->bd_disk)) {79 mutex_unlock(&bdev->bd_disk->open_mutex);80 return -ENODEV;81 }82 kobject_get(bdev->bd_holder_dir);83 mutex_unlock(&bdev->bd_disk->open_mutex);84 85 mutex_lock(&blk_holder_mutex);86 WARN_ON_ONCE(!bdev->bd_holder);87 88 holder = bd_find_holder_disk(bdev, disk);89 if (holder) {90 kobject_put(bdev->bd_holder_dir);91 holder->refcnt++;92 goto out_unlock;93 }94 95 holder = kzalloc(sizeof(*holder), GFP_KERNEL);96 if (!holder) {97 ret = -ENOMEM;98 goto out_unlock;99 }100 101 INIT_LIST_HEAD(&holder->list);102 holder->refcnt = 1;103 holder->holder_dir = bdev->bd_holder_dir;104 105 ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));106 if (ret)107 goto out_free_holder;108 ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);109 if (ret)110 goto out_del_symlink;111 list_add(&holder->list, &disk->slave_bdevs);112 113 mutex_unlock(&blk_holder_mutex);114 return 0;115 116out_del_symlink:117 del_symlink(disk->slave_dir, bdev_kobj(bdev));118out_free_holder:119 kfree(holder);120out_unlock:121 mutex_unlock(&blk_holder_mutex);122 if (ret)123 kobject_put(bdev->bd_holder_dir);124 return ret;125}126EXPORT_SYMBOL_GPL(bd_link_disk_holder);127 128/**129 * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()130 * @bdev: the calimed slave bdev131 * @disk: the holding disk132 *133 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.134 *135 * CONTEXT:136 * Might sleep.137 */138void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)139{140 struct bd_holder_disk *holder;141 142 if (WARN_ON_ONCE(!disk->slave_dir))143 return;144 145 mutex_lock(&blk_holder_mutex);146 holder = bd_find_holder_disk(bdev, disk);147 if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {148 del_symlink(disk->slave_dir, bdev_kobj(bdev));149 del_symlink(holder->holder_dir, &disk_to_dev(disk)->kobj);150 kobject_put(holder->holder_dir);151 list_del_init(&holder->list);152 kfree(holder);153 }154 mutex_unlock(&blk_holder_mutex);155}156EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);157