Commit eec38f5d authored by John Groves's avatar John Groves Committed by Ira Weiny
Browse files

dax: Add fs_dax_get() func to prepare dax for fs-dax usage 



The fs_dax_get() function should be called by fs-dax file systems after
opening a fsdev dax device. This adds holder_operations, which provides
a memory failure callback path and effects exclusivity between callers
of fs_dax_get().

fs_dax_get() is specific to fsdev_dax, so it checks the driver type
(which required touching bus.[ch]). fs_dax_get() fails if fsdev_dax is
not bound to the memory.

This function serves the same role as fs_dax_get_by_bdev(), which dax
file systems call after opening the pmem block device.

This can't be located in fsdev.c because struct dax_device is opaque
there.

This will be called by fs/fuse/famfs.c in a subsequent commit.

Reviewed-by: default avatarJonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: default avatarDave Jiang <dave.jiang@intel.com>
Signed-off-by: default avatarJohn Groves <john@groves.net>
Link: https://patch.msgid.link/0100019d311d8750-75395c22-031b-4d5f-aebe-790dca656b87-000000@email.amazonses.com


Signed-off-by: default avatarIra Weiny <ira.weiny@intel.com>
parent 700ecbc1

drivers/dax/bus.c

+0 −2
Original line number Diff line number Diff line
@@ -39,8 +39,6 @@ static int dax_bus_uevent(const struct device *dev, struct kobj_uevent_env *env) 
	return add_uevent_var(env, "MODALIAS=" DAX_DEVICE_MODALIAS_FMT, 0);

}



#define to_dax_drv(__drv)	container_of_const(__drv, struct dax_device_driver, drv)



static struct dax_id *__dax_match_id(const struct dax_device_driver *dax_drv,

		const char *dev_name)

{

drivers/dax/bus.h

+2 −0
Original line number Diff line number Diff line
@@ -42,6 +42,8 @@ struct dax_device_driver { 
	void (*remove)(struct dev_dax *dev);

};



#define to_dax_drv(__drv) container_of_const(__drv, struct dax_device_driver, drv)



int __dax_driver_register(struct dax_device_driver *dax_drv,

		struct module *module, const char *mod_name);

#define dax_driver_register(driver) \

drivers/dax/super.c

+65 −1
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/fs.h>

#include <linux/cacheinfo.h>

#include "dax-private.h"

#include "bus.h"



/**

 * struct dax_device - anchor object for dax services
@@ -111,6 +112,10 @@ struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off, 
}

EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);



#endif /* CONFIG_BLOCK && CONFIG_FS_DAX */



#if IS_ENABLED(CONFIG_FS_DAX)



void fs_put_dax(struct dax_device *dax_dev, void *holder)

{

	if (dax_dev && holder &&
@@ -119,7 +124,66 @@ void fs_put_dax(struct dax_device *dax_dev, void *holder) 
	put_dax(dax_dev);

}

EXPORT_SYMBOL_GPL(fs_put_dax);

#endif /* CONFIG_BLOCK && CONFIG_FS_DAX */



/**

 * fs_dax_get() - get ownership of a devdax via holder/holder_ops

 *

 * fs-dax file systems call this function to prepare to use a devdax device for

 * fsdax. This is like fs_dax_get_by_bdev(), but the caller already has struct

 * dev_dax (and there is no bdev). The holder makes this exclusive.

 *

 * @dax_dev: dev to be prepared for fs-dax usage

 * @holder: filesystem or mapped device inside the dax_device

 * @hops: operations for the inner holder

 *

 * Returns: 0 on success, <0 on failure

 */

int fs_dax_get(struct dax_device *dax_dev, void *holder,

	const struct dax_holder_operations *hops)

{

	struct dev_dax *dev_dax;

	struct dax_device_driver *dax_drv;

	int id;



	id = dax_read_lock();

	if (!dax_dev || !dax_alive(dax_dev) || !igrab(&dax_dev->inode)) {

		dax_read_unlock(id);

		return -ENODEV;

	}

	dax_read_unlock(id);



	/* Verify the device is bound to fsdev_dax driver */

	dev_dax = dax_get_private(dax_dev);

	if (!dev_dax) {

		iput(&dax_dev->inode);

		return -ENODEV;

	}



	device_lock(&dev_dax->dev);

	if (!dev_dax->dev.driver) {

		device_unlock(&dev_dax->dev);

		iput(&dax_dev->inode);

		return -ENODEV;

	}

	dax_drv = to_dax_drv(dev_dax->dev.driver);

	if (dax_drv->type != DAXDRV_FSDEV_TYPE) {

		device_unlock(&dev_dax->dev);

		iput(&dax_dev->inode);

		return -EOPNOTSUPP;

	}

	device_unlock(&dev_dax->dev);



	if (cmpxchg(&dax_dev->holder_data, NULL, holder)) {

		iput(&dax_dev->inode);

		return -EBUSY;

	}



	dax_dev->holder_ops = hops;



	return 0;

}

EXPORT_SYMBOL_GPL(fs_dax_get);

#endif /* CONFIG_FS_DAX */



enum dax_device_flags {

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

include/linux/dax.h

+12 −4
Original line number Diff line number Diff line
@@ -130,7 +130,6 @@ int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk); 
void dax_remove_host(struct gendisk *disk);

struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off,

		void *holder, const struct dax_holder_operations *ops);

void fs_put_dax(struct dax_device *dax_dev, void *holder);

#else

static inline int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk)

{
@@ -145,12 +144,12 @@ static inline struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, 
{

	return NULL;

}

static inline void fs_put_dax(struct dax_device *dax_dev, void *holder)

{

}

#endif /* CONFIG_BLOCK && CONFIG_FS_DAX */



#if IS_ENABLED(CONFIG_FS_DAX)

void fs_put_dax(struct dax_device *dax_dev, void *holder);

int fs_dax_get(struct dax_device *dax_dev, void *holder,

	       const struct dax_holder_operations *hops);

int dax_writeback_mapping_range(struct address_space *mapping,

		struct dax_device *dax_dev, struct writeback_control *wbc);

int dax_folio_reset_order(struct folio *folio);
@@ -164,6 +163,15 @@ dax_entry_t dax_lock_mapping_entry(struct address_space *mapping, 
void dax_unlock_mapping_entry(struct address_space *mapping,

		unsigned long index, dax_entry_t cookie);

#else

static inline void fs_put_dax(struct dax_device *dax_dev, void *holder)

{

}



static inline int fs_dax_get(struct dax_device *dax_dev, void *holder,

			     const struct dax_holder_operations *hops)

{

	return -EOPNOTSUPP;

}

static inline struct page *dax_layout_busy_page(struct address_space *mapping)

{

	return NULL;