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block: simplify holder symlink handling

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Code to manage symlinks in /sys/block/*/{holders|slaves} are overly
complex with multiple holder considerations, redundant extra
references to all involved kobjects, unused generic kobject holder
support and unnecessary mixup with bd_claim/release functionalities.

Strip it down to what's necessary (single gendisk holder) and make it
use a separate interface.  This is a step for cleaning up
bd_claim/release.  This patch makes dm-table slightly more complex but
it will be simplified again with further changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Brown <neilb@suse.de>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Cc: dm-devel@redhat.com
This commit is contained in:
Tejun Heo 2010-11-13 11:55:17 +01:00
parent 37004c42f7
commit e09b457bdb
4 changed files with 80 additions and 297 deletions
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23
drivers/md/dm-table.c
View File

@ -328,12 +328,22 @@ static int open_dev(struct dm_dev_internal *d, dev_t dev,
bdev = open_by_devnum(dev, d->dm_dev.mode);
if (IS_ERR(bdev))
return PTR_ERR(bdev);
r = bd_claim_by_disk(bdev, _claim_ptr, dm_disk(md));
if (r)
r = bd_claim(bdev, _claim_ptr);
if (r) {
blkdev_put(bdev, d->dm_dev.mode);
else
d->dm_dev.bdev = bdev;
return r;
return r;
}
r = bd_link_disk_holder(bdev, dm_disk(md));
if (r) {
bd_release(bdev);
blkdev_put(bdev, d->dm_dev.mode);
return r;
}
d->dm_dev.bdev = bdev;
return 0;
}
/*
@ -344,7 +354,8 @@ static void close_dev(struct dm_dev_internal *d, struct mapped_device *md)
if (!d->dm_dev.bdev)
return;
bd_release_from_disk(d->dm_dev.bdev, dm_disk(md));
bd_unlink_disk_holder(d->dm_dev.bdev);
bd_release(d->dm_dev.bdev);
blkdev_put(d->dm_dev.bdev, d->dm_dev.mode);
d->dm_dev.bdev = NULL;
}

4
drivers/md/md.c
View File

@ -1880,7 +1880,7 @@ static int bind_rdev_to_array(mdk_rdev_t * rdev, mddev_t * mddev)
rdev->sysfs_state = sysfs_get_dirent_safe(rdev->kobj.sd, "state");
list_add_rcu(&rdev->same_set, &mddev->disks);
bd_claim_by_disk(rdev->bdev, rdev->bdev->bd_holder, mddev->gendisk);
bd_link_disk_holder(rdev->bdev, mddev->gendisk);
/* May as well allow recovery to be retried once */
mddev->recovery_disabled = 0;
@ -1907,7 +1907,7 @@ static void unbind_rdev_from_array(mdk_rdev_t * rdev)
MD_BUG();
return;
}
bd_release_from_disk(rdev->bdev, rdev->mddev->gendisk);
bd_unlink_disk_holder(rdev->bdev);
list_del_rcu(&rdev->same_set);
printk(KERN_INFO "md: unbind<%s>\n", bdevname(rdev->bdev,b));
rdev->mddev = NULL;

334
fs/block_dev.c
View File

@ -426,9 +426,6 @@ static void init_once(void *foo)
mutex_init(&bdev->bd_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);
/* Initialize mutex for freeze. */
mutex_init(&bdev->bd_fsfreeze_mutex);
@ -881,314 +878,83 @@ 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 int add_symlink(struct kobject *from, struct kobject *to)
{
if (!from || !to)
return 0;
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 = kobject_get(&part_to_dev(bdev->bd_part)->kobj);
if (!bo->sdev)
goto fail_put_hdev;
bo->hdir = kobject_get(bdev->bd_part->holder_dir);
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);
}
/**
* find_bd_holder - find matching struct bd_holder from the block device
* bd_link_disk_holder - create symlinks between holding disk and slave bdev
* @bdev: the claimed slave bdev
* @disk: the holding disk
*
* @bdev: struct block device to be searched
* @bo: target struct bd_holder
* This functions creates the following sysfs symlinks.
*
* Returns matching entry with @bo in @bdev->bd_holder_list.
* If found, increment the reference count and return the pointer.
* If not found, returns NULL.
* - 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.
*/
static struct bd_holder *find_bd_holder(struct block_device *bdev,
struct bd_holder *bo)
int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
{
struct bd_holder *tmp;
list_for_each_entry(tmp, &bdev->bd_holder_list, list)
if (tmp->sdir == bo->sdir) {
tmp->count++;
return tmp;
}
return NULL;
}
/**
* 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()
*
* Add @bo to @bdev->bd_holder_list, create symlinks.
*
* Returns 0 if symlinks are created.
* Returns -ve if something fails.
*/
static int add_bd_holder(struct block_device *bdev, struct bd_holder *bo)
{
int err;
if (!bo)
return -EINVAL;
if (!bd_holder_grab_dirs(bdev, bo))
return -EBUSY;
err = add_symlink(bo->sdir, bo->sdev);
if (err)
return err;
err = add_symlink(bo->hdir, bo->hdev);
if (err) {
del_symlink(bo->sdir, bo->sdev);
return err;
}
list_add_tail(&bo->list, &bdev->bd_holder_list);
return 0;
}
/**
* 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 err;
struct bd_holder *bo, *found;
if (!kobj)
return -EINVAL;
bo = alloc_bd_holder(kobj);
if (!bo)
return -ENOMEM;
int ret = 0;
mutex_lock(&bdev->bd_mutex);
err = bd_claim(bdev, holder);
if (err)
goto fail;
WARN_ON_ONCE(!bdev->bd_holder || bdev->bd_holder_disk);
found = find_bd_holder(bdev, bo);
if (found)
goto fail;
/* FIXME: remove the following once add_disk() handles errors */
if (WARN_ON(!disk->slave_dir || !bdev->bd_part->holder_dir))
goto out_unlock;
err = add_bd_holder(bdev, bo);
if (err)
bd_release(bdev);
else
bo = NULL;
fail:
ret = add_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
if (ret)
goto out_unlock;
ret = add_symlink(bdev->bd_part->holder_dir, &disk_to_dev(disk)->kobj);
if (ret) {
del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
goto out_unlock;
}
bdev->bd_holder_disk = disk;
out_unlock:
mutex_unlock(&bdev->bd_mutex);
free_bd_holder(bo);
return err;
return ret;
}
EXPORT_SYMBOL_GPL(bd_link_disk_holder);
/**
* 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)
void bd_unlink_disk_holder(struct block_device *bdev)
{
if (!kobj)
struct gendisk *disk = bdev->bd_holder_disk;
bdev->bd_holder_disk = NULL;
if (!disk)
return;
mutex_lock(&bdev->bd_mutex);
bd_release(bdev);
free_bd_holder(del_bd_holder(bdev, kobj));
mutex_unlock(&bdev->bd_mutex);
del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
del_symlink(bdev->bd_part->holder_dir, &disk_to_dev(disk)->kobj);
}
/**
* 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);
EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
#endif
/*

16
include/linux/fs.h
View File

@ -663,7 +663,7 @@ struct block_device {
void * bd_holder;
int bd_holders;
#ifdef CONFIG_SYSFS
struct list_head bd_holder_list;
struct gendisk * bd_holder_disk; /* for sysfs slave linkng */
#endif
struct block_device * bd_contains;
unsigned bd_block_size;
@ -2042,11 +2042,17 @@ extern int blkdev_put(struct block_device *, fmode_t);
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 *);
extern int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk);
extern void bd_unlink_disk_holder(struct block_device *bdev);
#else
#define bd_claim_by_disk(bdev, holder, disk) bd_claim(bdev, holder)
#define bd_release_from_disk(bdev, disk) bd_release(bdev)
static inline int bd_link_disk_holder(struct block_device *bdev,
struct gendisk *disk)
{
return 0;
}
static inline void bd_unlink_disk_holder(struct block_device *bdev)
{
}
#endif
#endif