155 lines
3.8 KiB
C
155 lines
3.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/blkdev.h>
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#include <linux/slab.h>
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struct bd_holder_disk {
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struct list_head list;
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struct kobject *holder_dir;
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int refcnt;
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};
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static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
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struct gendisk *disk)
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{
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struct bd_holder_disk *holder;
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list_for_each_entry(holder, &disk->slave_bdevs, list)
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if (holder->holder_dir == bdev->bd_holder_dir)
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return holder;
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return NULL;
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}
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static int add_symlink(struct kobject *from, struct kobject *to)
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{
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return sysfs_create_link(from, to, kobject_name(to));
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}
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static void del_symlink(struct kobject *from, struct kobject *to)
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{
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sysfs_remove_link(from, kobject_name(to));
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}
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/**
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* bd_link_disk_holder - create symlinks between holding disk and slave bdev
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* @bdev: the claimed slave bdev
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* @disk: the holding disk
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*
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* DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
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*
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* This functions creates the following sysfs symlinks.
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*
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* - from "slaves" directory of the holder @disk to the claimed @bdev
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* - from "holders" directory of the @bdev to the holder @disk
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*
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* For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
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* passed to bd_link_disk_holder(), then:
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*
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* /sys/block/dm-0/slaves/sda --> /sys/block/sda
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* /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
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*
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* The caller must have claimed @bdev before calling this function and
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* ensure that both @bdev and @disk are valid during the creation and
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* lifetime of these symlinks.
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*
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* CONTEXT:
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* Might sleep.
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*
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* RETURNS:
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* 0 on success, -errno on failure.
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*/
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int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
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{
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struct bd_holder_disk *holder;
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int ret = 0;
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if (WARN_ON_ONCE(!disk->slave_dir))
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return -EINVAL;
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if (bdev->bd_disk == disk)
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return -EINVAL;
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/*
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* del_gendisk drops the initial reference to bd_holder_dir, so we
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* need to keep our own here to allow for cleanup past that point.
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*/
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mutex_lock(&bdev->bd_disk->open_mutex);
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if (!disk_live(bdev->bd_disk)) {
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mutex_unlock(&bdev->bd_disk->open_mutex);
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return -ENODEV;
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}
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kobject_get(bdev->bd_holder_dir);
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mutex_unlock(&bdev->bd_disk->open_mutex);
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mutex_lock(&disk->open_mutex);
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WARN_ON_ONCE(!bdev->bd_holder);
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holder = bd_find_holder_disk(bdev, disk);
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if (holder) {
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kobject_put(bdev->bd_holder_dir);
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holder->refcnt++;
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goto out_unlock;
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}
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holder = kzalloc(sizeof(*holder), GFP_KERNEL);
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if (!holder) {
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ret = -ENOMEM;
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goto out_unlock;
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}
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INIT_LIST_HEAD(&holder->list);
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holder->refcnt = 1;
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holder->holder_dir = bdev->bd_holder_dir;
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ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
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if (ret)
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goto out_free_holder;
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ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
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if (ret)
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goto out_del_symlink;
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list_add(&holder->list, &disk->slave_bdevs);
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mutex_unlock(&disk->open_mutex);
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return 0;
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out_del_symlink:
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del_symlink(disk->slave_dir, bdev_kobj(bdev));
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out_free_holder:
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kfree(holder);
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out_unlock:
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mutex_unlock(&disk->open_mutex);
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if (ret)
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kobject_put(bdev->bd_holder_dir);
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return ret;
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}
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EXPORT_SYMBOL_GPL(bd_link_disk_holder);
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/**
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* bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
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* @bdev: the calimed slave bdev
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* @disk: the holding disk
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*
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* DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
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*
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* CONTEXT:
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* Might sleep.
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*/
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void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
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{
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struct bd_holder_disk *holder;
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if (WARN_ON_ONCE(!disk->slave_dir))
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return;
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mutex_lock(&disk->open_mutex);
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holder = bd_find_holder_disk(bdev, disk);
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if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
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del_symlink(disk->slave_dir, bdev_kobj(bdev));
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del_symlink(holder->holder_dir, &disk_to_dev(disk)->kobj);
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kobject_put(holder->holder_dir);
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list_del_init(&holder->list);
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kfree(holder);
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}
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mutex_unlock(&disk->open_mutex);
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}
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EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
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