Commit 641dc636 authored by Jun'ichi Nomura's avatar Jun'ichi Nomura Committed by Linus Torvalds
Browse files

[PATCH] dm/md dependency tree in sysfs: bd_claim_by_kobject 



Adding bd_claim_by_kobject() function which takes kobject as additional
signature of holder device and creates sysfs symlinks between holder device
and claimed device.  bd_release_from_kobject() is a counterpart of
bd_claim_by_kobject.

Signed-off-by: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 10087368

fs/block_dev.c

+297 −0
Original line number Diff line number Diff line
@@ -266,6 +266,9 @@ static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags) 
		mutex_init(&bdev->bd_mount_mutex);

		INIT_LIST_HEAD(&bdev->bd_inodes);

		INIT_LIST_HEAD(&bdev->bd_list);

#ifdef CONFIG_SYSFS

		INIT_LIST_HEAD(&bdev->bd_holder_list);

#endif

		inode_init_once(&ei->vfs_inode);

	}

}
@@ -490,6 +493,300 @@ void bd_release(struct block_device *bdev) 


EXPORT_SYMBOL(bd_release);



#ifdef CONFIG_SYSFS

/*

 * Functions for bd_claim_by_kobject / bd_release_from_kobject

 *

 *     If a kobject is passed to bd_claim_by_kobject()

 *     and the kobject has a parent directory,

 *     following symlinks are created:

 *        o from the kobject to the claimed bdev

 *        o from "holders" directory of the bdev to the parent of the kobject

 *     bd_release_from_kobject() removes these symlinks.

 *

 *     Example:

 *        If /dev/dm-0 maps to /dev/sda, kobject corresponding to

 *        /sys/block/dm-0/slaves is passed to bd_claim_by_kobject(), then:

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

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

 */



static struct kobject *bdev_get_kobj(struct block_device *bdev)

{

	if (bdev->bd_contains != bdev)

		return kobject_get(&bdev->bd_part->kobj);

	else

		return kobject_get(&bdev->bd_disk->kobj);

}



static struct kobject *bdev_get_holder(struct block_device *bdev)

{

	if (bdev->bd_contains != bdev)

		return kobject_get(bdev->bd_part->holder_dir);

	else

		return kobject_get(bdev->bd_disk->holder_dir);

}



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

{

	if (!from || !to)

		return;

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

}



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

{

	if (!from || !to)

		return;

	sysfs_remove_link(from, kobject_name(to));

}



/*

 * 'struct bd_holder' contains pointers to kobjects symlinked by

 * bd_claim_by_kobject.

 * It's connected to bd_holder_list which is protected by bdev->bd_sem.

 */

struct bd_holder {

	struct list_head list;	/* chain of holders of the bdev */

	int count;		/* references from the holder */

	struct kobject *sdir;	/* holder object, e.g. "/block/dm-0/slaves" */

	struct kobject *hdev;	/* e.g. "/block/dm-0" */

	struct kobject *hdir;	/* e.g. "/block/sda/holders" */

	struct kobject *sdev;	/* e.g. "/block/sda" */

};



/*

 * Get references of related kobjects at once.

 * Returns 1 on success. 0 on failure.

 *

 * Should call bd_holder_release_dirs() after successful use.

 */

static int bd_holder_grab_dirs(struct block_device *bdev,

			struct bd_holder *bo)

{

	if (!bdev || !bo)

		return 0;



	bo->sdir = kobject_get(bo->sdir);

	if (!bo->sdir)

		return 0;



	bo->hdev = kobject_get(bo->sdir->parent);

	if (!bo->hdev)

		goto fail_put_sdir;



	bo->sdev = bdev_get_kobj(bdev);

	if (!bo->sdev)

		goto fail_put_hdev;



	bo->hdir = bdev_get_holder(bdev);

	if (!bo->hdir)

		goto fail_put_sdev;



	return 1;



fail_put_sdev:

	kobject_put(bo->sdev);

fail_put_hdev:

	kobject_put(bo->hdev);

fail_put_sdir:

	kobject_put(bo->sdir);



	return 0;

}



/* Put references of related kobjects at once. */

static void bd_holder_release_dirs(struct bd_holder *bo)

{

	kobject_put(bo->hdir);

	kobject_put(bo->sdev);

	kobject_put(bo->hdev);

	kobject_put(bo->sdir);

}



static struct bd_holder *alloc_bd_holder(struct kobject *kobj)

{

	struct bd_holder *bo;



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

	if (!bo)

		return NULL;



	bo->count = 1;

	bo->sdir = kobj;



	return bo;

}



static void free_bd_holder(struct bd_holder *bo)

{

	kfree(bo);

}



/**

 * add_bd_holder - create sysfs symlinks for bd_claim() relationship

 *

 * @bdev:	block device to be bd_claimed

 * @bo:		preallocated and initialized by alloc_bd_holder()

 *

 * If there is no matching entry with @bo in @bdev->bd_holder_list,

 * add @bo to the list, create symlinks.

 *

 * Returns 1 if @bo was added to the list.

 * Returns 0 if @bo wasn't used by any reason and should be freed.

 */

static int add_bd_holder(struct block_device *bdev, struct bd_holder *bo)

{

	struct bd_holder *tmp;



	if (!bo)

		return 0;



	list_for_each_entry(tmp, &bdev->bd_holder_list, list) {

		if (tmp->sdir == bo->sdir) {

			tmp->count++;

			return 0;

		}

	}



	if (!bd_holder_grab_dirs(bdev, bo))

		return 0;



	add_symlink(bo->sdir, bo->sdev);

	add_symlink(bo->hdir, bo->hdev);

	list_add_tail(&bo->list, &bdev->bd_holder_list);

	return 1;

}



/**

 * del_bd_holder - delete sysfs symlinks for bd_claim() relationship

 *

 * @bdev:	block device to be bd_claimed

 * @kobj:	holder's kobject

 *

 * If there is matching entry with @kobj in @bdev->bd_holder_list

 * and no other bd_claim() from the same kobject,

 * remove the struct bd_holder from the list, delete symlinks for it.

 *

 * Returns a pointer to the struct bd_holder when it's removed from the list

 * and ready to be freed.

 * Returns NULL if matching claim isn't found or there is other bd_claim()

 * by the same kobject.

 */

static struct bd_holder *del_bd_holder(struct block_device *bdev,

					struct kobject *kobj)

{

	struct bd_holder *bo;



	list_for_each_entry(bo, &bdev->bd_holder_list, list) {

		if (bo->sdir == kobj) {

			bo->count--;

			BUG_ON(bo->count < 0);

			if (!bo->count) {

				list_del(&bo->list);

				del_symlink(bo->sdir, bo->sdev);

				del_symlink(bo->hdir, bo->hdev);

				bd_holder_release_dirs(bo);

				return bo;

			}

			break;

		}

	}



	return NULL;

}



/**

 * bd_claim_by_kobject - bd_claim() with additional kobject signature

 *

 * @bdev:	block device to be claimed

 * @holder:	holder's signature

 * @kobj:	holder's kobject

 *

 * Do bd_claim() and if it succeeds, create sysfs symlinks between

 * the bdev and the holder's kobject.

 * Use bd_release_from_kobject() when relesing the claimed bdev.

 *

 * Returns 0 on success. (same as bd_claim())

 * Returns errno on failure.

 */

static int bd_claim_by_kobject(struct block_device *bdev, void *holder,

				struct kobject *kobj)

{

	int res;

	struct bd_holder *bo;



	if (!kobj)

		return -EINVAL;



	bo = alloc_bd_holder(kobj);

	if (!bo)

		return -ENOMEM;



	down(&bdev->bd_sem);

	res = bd_claim(bdev, holder);

	if (res || !add_bd_holder(bdev, bo))

		free_bd_holder(bo);

	up(&bdev->bd_sem);



	return res;

}



/**

 * bd_release_from_kobject - bd_release() with additional kobject signature

 *

 * @bdev:	block device to be released

 * @kobj:	holder's kobject

 *

 * Do bd_release() and remove sysfs symlinks created by bd_claim_by_kobject().

 */

static void bd_release_from_kobject(struct block_device *bdev,

					struct kobject *kobj)

{

	struct bd_holder *bo;



	if (!kobj)

		return;



	down(&bdev->bd_sem);

	bd_release(bdev);

	if ((bo = del_bd_holder(bdev, kobj)))

		free_bd_holder(bo);

	up(&bdev->bd_sem);

}



/**

 * bd_claim_by_disk - wrapper function for bd_claim_by_kobject()

 *

 * @bdev:	block device to be claimed

 * @holder:	holder's signature

 * @disk:	holder's gendisk

 *

 * Call bd_claim_by_kobject() with getting @disk->slave_dir.

 */

int bd_claim_by_disk(struct block_device *bdev, void *holder,

			struct gendisk *disk)

{

	return bd_claim_by_kobject(bdev, holder, kobject_get(disk->slave_dir));

}

EXPORT_SYMBOL_GPL(bd_claim_by_disk);



/**

 * bd_release_from_disk - wrapper function for bd_release_from_kobject()

 *

 * @bdev:	block device to be claimed

 * @disk:	holder's gendisk

 *

 * Call bd_release_from_kobject() and put @disk->slave_dir.

 */

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

{

	bd_release_from_kobject(bdev, disk->slave_dir);

	kobject_put(disk->slave_dir);

}

EXPORT_SYMBOL_GPL(bd_release_from_disk);

#endif



/*

 * Tries to open block device by device number.  Use it ONLY if you

 * really do not have anything better - i.e. when you are behind a

include/linux/fs.h

+10 −0
Original line number Diff line number Diff line
@@ -410,6 +410,9 @@ struct block_device { 
	struct list_head	bd_inodes;

	void *			bd_holder;

	int			bd_holders;

#ifdef CONFIG_SYSFS

	struct list_head	bd_holder_list;

#endif

	struct block_device *	bd_contains;

	unsigned		bd_block_size;

	struct hd_struct *	bd_part;
@@ -1399,6 +1402,13 @@ extern int blkdev_get(struct block_device *, mode_t, unsigned); 
extern int blkdev_put(struct block_device *);

extern int bd_claim(struct block_device *, void *);

extern void bd_release(struct block_device *);

#ifdef CONFIG_SYSFS

extern int bd_claim_by_disk(struct block_device *, void *, struct gendisk *);

extern void bd_release_from_disk(struct block_device *, struct gendisk *);

#else

#define bd_claim_by_disk(bdev, holder, disk)	bd_claim(bdev, holder)

#define bd_release_from_disk(bdev, disk)	bd_release(bdev)

#endif



/* fs/char_dev.c */

extern int alloc_chrdev_region(dev_t *, unsigned, unsigned, const char *);

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