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Commit 72058005 authored by Dan Williams's avatar Dan Williams
Browse files

dax: add a facility to lookup a dax device by 'host' device name 



For the current block_device based filesystem-dax path, we need a way
for it to lookup the dax_device associated with a block_device. Add a
'host' property of a dax_device that can be used for this purpose. It is
a free form string, but for a dax_device associated with a block device
it is the bdev name.

This is a stop-gap until filesystems are able to mount on a dax-inode
directly.

Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 7b6be844

drivers/dax/dax.h

+1 −1
Original line number Diff line number Diff line
@@ -13,7 +13,7 @@ 
#ifndef __DAX_H__

#define __DAX_H__

struct dax_device;

struct dax_device *alloc_dax(void *private);

struct dax_device *alloc_dax(void *private, const char *host);

void put_dax(struct dax_device *dax_dev);

bool dax_alive(struct dax_device *dax_dev);

void kill_dax(struct dax_device *dax_dev);

drivers/dax/device.c

+1 −1
Original line number Diff line number Diff line
@@ -645,7 +645,7 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region, 
		goto err_id;

	}



	dax_dev = alloc_dax(dev_dax);

	dax_dev = alloc_dax(dev_dax, NULL);

	if (!dax_dev)

		goto err_dax;

drivers/dax/super.c

+83 −4
Original line number Diff line number Diff line
@@ -30,6 +30,10 @@ static DEFINE_IDA(dax_minor_ida); 
static struct kmem_cache *dax_cache __read_mostly;

static struct super_block *dax_superblock __read_mostly;



#define DAX_HASH_SIZE (PAGE_SIZE / sizeof(struct hlist_head))

static struct hlist_head dax_host_list[DAX_HASH_SIZE];

static DEFINE_SPINLOCK(dax_host_lock);



int dax_read_lock(void)

{

	return srcu_read_lock(&dax_srcu);
@@ -46,12 +50,15 @@ EXPORT_SYMBOL_GPL(dax_read_unlock); 
 * struct dax_device - anchor object for dax services

 * @inode: core vfs

 * @cdev: optional character interface for "device dax"

 * @host: optional name for lookups where the device path is not available

 * @private: dax driver private data

 * @alive: !alive + rcu grace period == no new operations / mappings

 */

struct dax_device {

	struct hlist_node list;

	struct inode inode;

	struct cdev cdev;

	const char *host;

	void *private;

	bool alive;

};
@@ -63,6 +70,11 @@ bool dax_alive(struct dax_device *dax_dev) 
}

EXPORT_SYMBOL_GPL(dax_alive);



static int dax_host_hash(const char *host)

{

	return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE;

}



/*

 * Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring

 * that any fault handlers or operations that might have seen
@@ -75,7 +87,13 @@ void kill_dax(struct dax_device *dax_dev) 
		return;



	dax_dev->alive = false;



	synchronize_srcu(&dax_srcu);



	spin_lock(&dax_host_lock);

	hlist_del_init(&dax_dev->list);

	spin_unlock(&dax_host_lock);



	dax_dev->private = NULL;

}

EXPORT_SYMBOL_GPL(kill_dax);
@@ -98,6 +116,8 @@ static void dax_i_callback(struct rcu_head *head) 
	struct inode *inode = container_of(head, struct inode, i_rcu);

	struct dax_device *dax_dev = to_dax_dev(inode);



	kfree(dax_dev->host);

	dax_dev->host = NULL;

	ida_simple_remove(&dax_minor_ida, MINOR(inode->i_rdev));

	kmem_cache_free(dax_cache, dax_dev);

}
@@ -169,26 +189,53 @@ static struct dax_device *dax_dev_get(dev_t devt) 
	return dax_dev;

}



struct dax_device *alloc_dax(void *private)

static void dax_add_host(struct dax_device *dax_dev, const char *host)

{

	int hash;



	/*

	 * Unconditionally init dax_dev since it's coming from a

	 * non-zeroed slab cache

	 */

	INIT_HLIST_NODE(&dax_dev->list);

	dax_dev->host = host;

	if (!host)

		return;



	hash = dax_host_hash(host);

	spin_lock(&dax_host_lock);

	hlist_add_head(&dax_dev->list, &dax_host_list[hash]);

	spin_unlock(&dax_host_lock);

}



struct dax_device *alloc_dax(void *private, const char *__host)

{

	struct dax_device *dax_dev;

	const char *host;

	dev_t devt;

	int minor;



	host = kstrdup(__host, GFP_KERNEL);

	if (__host && !host)

		return NULL;



	minor = ida_simple_get(&dax_minor_ida, 0, nr_dax, GFP_KERNEL);

	if (minor < 0)

		return NULL;

		goto err_minor;



	devt = MKDEV(MAJOR(dax_devt), minor);

	dax_dev = dax_dev_get(devt);

	if (!dax_dev)

		goto err_inode;

		goto err_dev;



	dax_add_host(dax_dev, host);

	dax_dev->private = private;

	return dax_dev;



 err_inode:

 err_dev:

	ida_simple_remove(&dax_minor_ida, minor);

 err_minor:

	kfree(host);

	return NULL;

}

EXPORT_SYMBOL_GPL(alloc_dax);
@@ -201,6 +248,38 @@ void put_dax(struct dax_device *dax_dev) 
}

EXPORT_SYMBOL_GPL(put_dax);



/**

 * dax_get_by_host() - temporary lookup mechanism for filesystem-dax

 * @host: alternate name for the device registered by a dax driver

 */

struct dax_device *dax_get_by_host(const char *host)

{

	struct dax_device *dax_dev, *found = NULL;

	int hash, id;



	if (!host)

		return NULL;



	hash = dax_host_hash(host);



	id = dax_read_lock();

	spin_lock(&dax_host_lock);

	hlist_for_each_entry(dax_dev, &dax_host_list[hash], list) {

		if (!dax_alive(dax_dev)

				|| strcmp(host, dax_dev->host) != 0)

			continue;



		if (igrab(&dax_dev->inode))

			found = dax_dev;

		break;

	}

	spin_unlock(&dax_host_lock);

	dax_read_unlock(id);



	return found;

}

EXPORT_SYMBOL_GPL(dax_get_by_host);



/**

 * inode_dax: convert a public inode into its dax_dev

 * @inode: An inode with i_cdev pointing to a dax_dev

include/linux/dax.h

+1 −0
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ struct iomap_ops; 


int dax_read_lock(void);

void dax_read_unlock(int id);

struct dax_device *dax_get_by_host(const char *host);



/*

 * We use lowest available bit in exceptional entry for locking, one bit for