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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 11-01-2010, 03:15 PM
Tejun Heo
 
Default block: simplify holder symlink handling

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>
Cc: Neil Brown <neilb@suse.de>
Cc: dm-devel@redhat.com
---
drivers/md/dm-table.c | 23 +++-
drivers/md/md.c | 4 +-
fs/block_dev.c | 322 +++++++------------------------------------------
include/linux/fs.h | 16 ++-
4 files changed, 74 insertions(+), 291 deletions(-)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 90267f8..2c876ff 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -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;
}
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 4e957f3..c47644f 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -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>
", bdevname(rdev->bdev,b));
rdev->mddev = NULL;
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 06e8ff1..9329068 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -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.
- */
-static struct bd_holder *find_bd_holder(struct block_device *bdev,
- struct bd_holder *bo)
-{
- 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
+ * - from "slaves" directory of the holder @disk to the claimed @bdev
+ * - from "holders" directory of the @bdev to the holder @disk
*
- * @bdev: block device to be bd_claimed
- * @bo: preallocated and initialized by alloc_bd_holder()
+ * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
+ * passed to bd_link_disk_holder(), then:
*
- * Add @bo to @bdev->bd_holder_list, create symlinks.
+ * /sys/block/dm-0/slaves/sda --> /sys/block/sda
+ * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
*
- * 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
+ * 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.
*
- * 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.
+ * CONTEXT:
+ * Might sleep.
*
- * Returns 0 on success. (same as bd_claim())
- * Returns errno on failure.
+ * RETURNS:
+ * 0 on success, -errno on failure.
*/
-static int bd_claim_by_kobject(struct block_device *bdev, void *holder,
- struct kobject *kobj)
+int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
{
- 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:
- mutex_unlock(&bdev->bd_mutex);
- free_bd_holder(bo);
- return err;
-}
+ ret = add_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
+ if (ret)
+ goto out_unlock;

-/**
- * 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)
-{
- if (!kobj)
- return;
+ 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;
+ }

- mutex_lock(&bdev->bd_mutex);
- bd_release(bdev);
- free_bd_holder(del_bd_holder(bdev, kobj));
+ bdev->bd_holder_disk = disk;
+out_unlock:
mutex_unlock(&bdev->bd_mutex);
+ return ret;
}
+EXPORT_SYMBOL_GPL(bd_link_disk_holder);

-/**
- * 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)
+void bd_unlink_disk_holder(struct block_device *bdev)
{
- return bd_claim_by_kobject(bdev, holder, kobject_get(disk->slave_dir));
-}
-EXPORT_SYMBOL_GPL(bd_claim_by_disk);
+ struct gendisk *disk = bdev->bd_holder_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);
+ bdev->bd_holder_disk = NULL;
+ if (!disk)
+ return;
+
+ del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
+ del_symlink(bdev->bd_part->holder_dir, &disk_to_dev(disk)->kobj);
}
-EXPORT_SYMBOL_GPL(bd_release_from_disk);
+EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
#endif

/*
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1eb2939..b361848 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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;
@@ -2043,11 +2043,17 @@ 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

--
1.7.1

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Old 11-04-2010, 02:06 PM
Mike Snitzer
 
Default block: simplify holder symlink handling

On Mon, Nov 01 2010 at 12:15pm -0400,
Tejun Heo <tj@kernel.org> wrote:

> 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>
> Cc: Neil Brown <neilb@suse.de>
> Cc: dm-devel@redhat.com

Acked-by: Mike Snitzer <snitzer@redhat.com>

> ---
> drivers/md/dm-table.c | 23 +++-
> drivers/md/md.c | 4 +-
> fs/block_dev.c | 322 +++++++------------------------------------------
> include/linux/fs.h | 16 ++-
> 4 files changed, 74 insertions(+), 291 deletions(-)
>
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 90267f8..2c876ff 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -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;
> }

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