fs/btrfs/volumes.h - kernel/msm-4.19 - Gitiles

 /*
  * Copyright (C) 2007 Oracle.  All rights reserved.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public
  * License v2 as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License for more details.
  *
  * You should have received a copy of the GNU General Public
  * License along with this program; if not, write to the
  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  * Boston, MA 021110-1307, USA.
  */

 #ifndef __BTRFS_VOLUMES_
 #define __BTRFS_VOLUMES_

 #include <linux/bio.h>
 #include <linux/sort.h>
 #include <linux/btrfs.h>
 #include "async-thread.h"

 #define BTRFS_STRIPE_LEN	(64 * 1024)

 struct buffer_head;
 struct btrfs_pending_bios {
 	struct bio *head;
 	struct bio *tail;
 };

 struct btrfs_device {
 	struct list_head dev_list;
 	struct list_head dev_alloc_list;
 	struct btrfs_fs_devices *fs_devices;
 	struct btrfs_root *dev_root;

 	/* regular prio bios */
 	struct btrfs_pending_bios pending_bios;
 	/* WRITE_SYNC bios */
 	struct btrfs_pending_bios pending_sync_bios;

 	int running_pending;
 	u64 generation;

 	int writeable;
 	int in_fs_metadata;
 	int missing;
 	int can_discard;
 	int is_tgtdev_for_dev_replace;

 	spinlock_t io_lock;

 	struct block_device *bdev;

 	/* the mode sent to blkdev_get */
 	fmode_t mode;

 	struct rcu_string *name;

 	/* the internal btrfs device id */
 	u64 devid;

 	/* size of the device */
 	u64 total_bytes;

 	/* size of the disk */
 	u64 disk_total_bytes;

 	/* bytes used */
 	u64 bytes_used;

 	/* optimal io alignment for this device */
 	u32 io_align;

 	/* optimal io width for this device */
 	u32 io_width;

 	/* minimal io size for this device */
 	u32 sector_size;

 	/* type and info about this device */
 	u64 type;

 	/* physical drive uuid (or lvm uuid) */
 	u8 uuid[BTRFS_UUID_SIZE];

 	/* per-device scrub information */
 	struct scrub_ctx *scrub_device;

 	struct btrfs_work work;
 	struct rcu_head rcu;
 	struct work_struct rcu_work;

 	/* readahead state */
 	spinlock_t reada_lock;
 	atomic_t reada_in_flight;
 	u64 reada_next;
 	struct reada_zone *reada_curr_zone;
 	struct radix_tree_root reada_zones;
 	struct radix_tree_root reada_extents;

 	/* for sending down flush barriers */
 	struct bio *flush_bio;
 	struct completion flush_wait;
 	int nobarriers;

 	/* disk I/O failure stats. For detailed description refer to
 	 * enum btrfs_dev_stat_values in ioctl.h */
 	int dev_stats_valid;
 	int dev_stats_dirty; /* counters need to be written to disk */
 	atomic_t dev_stat_values[BTRFS_DEV_STAT_VALUES_MAX];
 };

 struct btrfs_fs_devices {
 	u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */

 	/* the device with this id has the most recent copy of the super */
 	u64 latest_devid;
 	u64 latest_trans;
 	u64 num_devices;
 	u64 open_devices;
 	u64 rw_devices;
 	u64 missing_devices;
 	u64 total_rw_bytes;
 	u64 num_can_discard;
 	u64 total_devices;
 	struct block_device *latest_bdev;

 	/* all of the devices in the FS, protected by a mutex
 	 * so we can safely walk it to write out the supers without
 	 * worrying about add/remove by the multi-device code
 	 */
 	struct mutex device_list_mutex;
 	struct list_head devices;

 	/* devices not currently being allocated */
 	struct list_head alloc_list;
 	struct list_head list;

 	struct btrfs_fs_devices *seed;
 	int seeding;

 	int opened;

 	/* set when we find or add a device that doesn't have the
 	 * nonrot flag set
 	 */
 	int rotating;
 };

 struct btrfs_bio_stripe {
 	struct btrfs_device *dev;
 	u64 physical;
 	u64 length; /* only used for discard mappings */
 };

 struct btrfs_bio;
 typedef void (btrfs_bio_end_io_t) (struct btrfs_bio *bio, int err);

 struct btrfs_bio {
 	atomic_t stripes_pending;
 	bio_end_io_t *end_io;
 	struct bio *orig_bio;
 	void *private;
 	atomic_t error;
 	int max_errors;
 	int num_stripes;
 	int mirror_num;
 	struct btrfs_bio_stripe stripes[];
 };

 struct btrfs_device_info {
 	struct btrfs_device *dev;
 	u64 dev_offset;
 	u64 max_avail;
 	u64 total_avail;
 };

 struct btrfs_raid_attr {
 	int sub_stripes;	/* sub_stripes info for map */
 	int dev_stripes;	/* stripes per dev */
 	int devs_max;		/* max devs to use */
 	int devs_min;		/* min devs needed */
 	int devs_increment;	/* ndevs has to be a multiple of this */
 	int ncopies;		/* how many copies to data has */
 };

 struct map_lookup {
 	u64 type;
 	int io_align;
 	int io_width;
 	int stripe_len;
 	int sector_size;
 	int num_stripes;
 	int sub_stripes;
 	struct btrfs_bio_stripe stripes[];
 };

 #define map_lookup_size(n) (sizeof(struct map_lookup) + \
 			    (sizeof(struct btrfs_bio_stripe) * (n)))

 /*
  * Restriper's general type filter
  */
 #define BTRFS_BALANCE_DATA		(1ULL << 0)
 #define BTRFS_BALANCE_SYSTEM		(1ULL << 1)
 #define BTRFS_BALANCE_METADATA		(1ULL << 2)

 #define BTRFS_BALANCE_TYPE_MASK		(BTRFS_BALANCE_DATA |	    \
 					 BTRFS_BALANCE_SYSTEM |	    \
 					 BTRFS_BALANCE_METADATA)

 #define BTRFS_BALANCE_FORCE		(1ULL << 3)
 #define BTRFS_BALANCE_RESUME		(1ULL << 4)

 /*
  * Balance filters
  */
 #define BTRFS_BALANCE_ARGS_PROFILES	(1ULL << 0)
 #define BTRFS_BALANCE_ARGS_USAGE	(1ULL << 1)
 #define BTRFS_BALANCE_ARGS_DEVID	(1ULL << 2)
 #define BTRFS_BALANCE_ARGS_DRANGE	(1ULL << 3)
 #define BTRFS_BALANCE_ARGS_VRANGE	(1ULL << 4)

 /*
  * Profile changing flags.  When SOFT is set we won't relocate chunk if
  * it already has the target profile (even though it may be
  * half-filled).
  */
 #define BTRFS_BALANCE_ARGS_CONVERT	(1ULL << 8)
 #define BTRFS_BALANCE_ARGS_SOFT		(1ULL << 9)

 struct btrfs_balance_args;
 struct btrfs_balance_progress;
 struct btrfs_balance_control {
 	struct btrfs_fs_info *fs_info;

 	struct btrfs_balance_args data;
 	struct btrfs_balance_args meta;
 	struct btrfs_balance_args sys;

 	u64 flags;

 	struct btrfs_balance_progress stat;
 };

 int btrfs_account_dev_extents_size(struct btrfs_device *device, u64 start,
 				   u64 end, u64 *length);

 #define btrfs_bio_size(n) (sizeof(struct btrfs_bio) + \
 			    (sizeof(struct btrfs_bio_stripe) * (n)))

 int btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
 		    u64 logical, u64 *length,
 		    struct btrfs_bio **bbio_ret, int mirror_num);
 int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
 		     u64 chunk_start, u64 physical, u64 devid,
 		     u64 **logical, int *naddrs, int *stripe_len);
 int btrfs_read_sys_array(struct btrfs_root *root);
 int btrfs_read_chunk_tree(struct btrfs_root *root);
 int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 		      struct btrfs_root *extent_root, u64 type);
 void btrfs_mapping_init(struct btrfs_mapping_tree *tree);
 void btrfs_mapping_tree_free(struct btrfs_mapping_tree *tree);
 int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
 		  int mirror_num, int async_submit);
 int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 		       fmode_t flags, void *holder);
 int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 			  struct btrfs_fs_devices **fs_devices_ret);
 int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
 void btrfs_close_extra_devices(struct btrfs_fs_info *fs_info,
 			       struct btrfs_fs_devices *fs_devices, int step);
 int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
 					 char *device_path,
 					 struct btrfs_device **device);
 int btrfs_rm_device(struct btrfs_root *root, char *device_path);
 void btrfs_cleanup_fs_uuids(void);
 int btrfs_num_copies(struct btrfs_fs_info *fs_info, u64 logical, u64 len);
 int btrfs_grow_device(struct btrfs_trans_handle *trans,
 		      struct btrfs_device *device, u64 new_size);
 struct btrfs_device *btrfs_find_device(struct btrfs_fs_info *fs_info, u64 devid,
 				       u8 *uuid, u8 *fsid);
 int btrfs_shrink_device(struct btrfs_device *device, u64 new_size);
 int btrfs_init_new_device(struct btrfs_root *root, char *path);
 int btrfs_init_dev_replace_tgtdev(struct btrfs_root *root, char *device_path,
 				  struct btrfs_device **device_out);
 int btrfs_balance(struct btrfs_balance_control *bctl,
 		  struct btrfs_ioctl_balance_args *bargs);
 int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info);
 int btrfs_recover_balance(struct btrfs_fs_info *fs_info);
 int btrfs_pause_balance(struct btrfs_fs_info *fs_info);
 int btrfs_cancel_balance(struct btrfs_fs_info *fs_info);
 int btrfs_chunk_readonly(struct btrfs_root *root, u64 chunk_offset);
 int find_free_dev_extent(struct btrfs_device *device, u64 num_bytes,
 			 u64 *start, u64 *max_avail);
 void btrfs_dev_stat_inc_and_print(struct btrfs_device *dev, int index);
 int btrfs_get_dev_stats(struct btrfs_root *root,
 			struct btrfs_ioctl_get_dev_stats *stats);
 int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info);
 int btrfs_run_dev_stats(struct btrfs_trans_handle *trans,
 			struct btrfs_fs_info *fs_info);
 void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info,
 				 struct btrfs_device *srcdev);
 void btrfs_destroy_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 				      struct btrfs_device *tgtdev);
 void btrfs_init_dev_replace_tgtdev_for_resume(struct btrfs_fs_info *fs_info,
 					      struct btrfs_device *tgtdev);
 int btrfs_scratch_superblock(struct btrfs_device *device);
 int btrfs_is_parity_mirror(struct btrfs_mapping_tree *map_tree,
 			   u64 logical, u64 len, int mirror_num);
 unsigned long btrfs_full_stripe_len(struct btrfs_root *root,
 				    struct btrfs_mapping_tree *map_tree,
 				    u64 logical);
 static inline void btrfs_dev_stat_inc(struct btrfs_device *dev,
 				      int index)
 {
 	atomic_inc(dev->dev_stat_values + index);
 	dev->dev_stats_dirty = 1;
 }

 static inline int btrfs_dev_stat_read(struct btrfs_device *dev,
 				      int index)
 {
 	return atomic_read(dev->dev_stat_values + index);
 }

 static inline int btrfs_dev_stat_read_and_reset(struct btrfs_device *dev,
 						int index)
 {
 	int ret;

 	ret = atomic_xchg(dev->dev_stat_values + index, 0);
 	dev->dev_stats_dirty = 1;
 	return ret;
 }

 static inline void btrfs_dev_stat_set(struct btrfs_device *dev,
 				      int index, unsigned long val)
 {
 	atomic_set(dev->dev_stat_values + index, val);
 	dev->dev_stats_dirty = 1;
 }

 static inline void btrfs_dev_stat_reset(struct btrfs_device *dev,
 					int index)
 {
 	btrfs_dev_stat_set(dev, index, 0);
 }
 #endif
	/*
	* Copyright (C) 2007 Oracle. All rights reserved.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public
	* License v2 as published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* General Public License for more details.
	*
	* You should have received a copy of the GNU General Public
	* License along with this program; if not, write to the
	* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	* Boston, MA 021110-1307, USA.
	*/

	#ifndef __BTRFS_VOLUMES_
	#define __BTRFS_VOLUMES_

	#include <linux/bio.h>
	#include <linux/sort.h>
	#include <linux/btrfs.h>
	#include "async-thread.h"

	#define BTRFS_STRIPE_LEN (64 * 1024)

	struct buffer_head;
	struct btrfs_pending_bios {
	struct bio *head;
	struct bio *tail;
	};

	struct btrfs_device {
	struct list_head dev_list;
	struct list_head dev_alloc_list;
	struct btrfs_fs_devices *fs_devices;
	struct btrfs_root *dev_root;

	/* regular prio bios */
	struct btrfs_pending_bios pending_bios;
	/* WRITE_SYNC bios */
	struct btrfs_pending_bios pending_sync_bios;

	int running_pending;
	u64 generation;

	int writeable;
	int in_fs_metadata;
	int missing;
	int can_discard;
	int is_tgtdev_for_dev_replace;

	spinlock_t io_lock;

	struct block_device *bdev;

	/* the mode sent to blkdev_get */
	fmode_t mode;

	struct rcu_string *name;

	/* the internal btrfs device id */
	u64 devid;

	/* size of the device */
	u64 total_bytes;

	/* size of the disk */
	u64 disk_total_bytes;

	/* bytes used */
	u64 bytes_used;

	/* optimal io alignment for this device */
	u32 io_align;

	/* optimal io width for this device */
	u32 io_width;

	/* minimal io size for this device */
	u32 sector_size;

	/* type and info about this device */
	u64 type;

	/* physical drive uuid (or lvm uuid) */
	u8 uuid[BTRFS_UUID_SIZE];

	/* per-device scrub information */
	struct scrub_ctx *scrub_device;

	struct btrfs_work work;
	struct rcu_head rcu;
	struct work_struct rcu_work;

	/* readahead state */
	spinlock_t reada_lock;
	atomic_t reada_in_flight;
	u64 reada_next;
	struct reada_zone *reada_curr_zone;
	struct radix_tree_root reada_zones;
	struct radix_tree_root reada_extents;

	/* for sending down flush barriers */
	struct bio *flush_bio;
	struct completion flush_wait;
	int nobarriers;

	/* disk I/O failure stats. For detailed description refer to
	* enum btrfs_dev_stat_values in ioctl.h */
	int dev_stats_valid;
	int dev_stats_dirty; /* counters need to be written to disk */
	atomic_t dev_stat_values[BTRFS_DEV_STAT_VALUES_MAX];
	};

	struct btrfs_fs_devices {
	u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */

	/* the device with this id has the most recent copy of the super */
	u64 latest_devid;
	u64 latest_trans;
	u64 num_devices;
	u64 open_devices;
	u64 rw_devices;
	u64 missing_devices;
	u64 total_rw_bytes;
	u64 num_can_discard;
	u64 total_devices;
	struct block_device *latest_bdev;

	/* all of the devices in the FS, protected by a mutex
	* so we can safely walk it to write out the supers without
	* worrying about add/remove by the multi-device code
	*/
	struct mutex device_list_mutex;
	struct list_head devices;

	/* devices not currently being allocated */
	struct list_head alloc_list;
	struct list_head list;

	struct btrfs_fs_devices *seed;
	int seeding;

	int opened;

	/* set when we find or add a device that doesn't have the
	* nonrot flag set
	*/
	int rotating;
	};

	struct btrfs_bio_stripe {
	struct btrfs_device *dev;
	u64 physical;
	u64 length; /* only used for discard mappings */
	};

	struct btrfs_bio;
	typedef void (btrfs_bio_end_io_t) (struct btrfs_bio *bio, int err);

	struct btrfs_bio {
	atomic_t stripes_pending;
	bio_end_io_t *end_io;
	struct bio *orig_bio;
	void *private;
	atomic_t error;
	int max_errors;
	int num_stripes;
	int mirror_num;
	struct btrfs_bio_stripe stripes[];
	};

	struct btrfs_device_info {
	struct btrfs_device *dev;
	u64 dev_offset;
	u64 max_avail;
	u64 total_avail;
	};

	struct btrfs_raid_attr {
	int sub_stripes; /* sub_stripes info for map */
	int dev_stripes; /* stripes per dev */
	int devs_max; /* max devs to use */
	int devs_min; /* min devs needed */
	int devs_increment; /* ndevs has to be a multiple of this */
	int ncopies; /* how many copies to data has */
	};

	struct map_lookup {
	u64 type;
	int io_align;
	int io_width;
	int stripe_len;
	int sector_size;
	int num_stripes;
	int sub_stripes;
	struct btrfs_bio_stripe stripes[];
	};

	#define map_lookup_size(n) (sizeof(struct map_lookup) + \
	(sizeof(struct btrfs_bio_stripe) * (n)))

	/*
	* Restriper's general type filter
	*/
	#define BTRFS_BALANCE_DATA (1ULL << 0)
	#define BTRFS_BALANCE_SYSTEM (1ULL << 1)
	#define BTRFS_BALANCE_METADATA (1ULL << 2)

	#define BTRFS_BALANCE_TYPE_MASK (BTRFS_BALANCE_DATA \| \
	BTRFS_BALANCE_SYSTEM \| \
	BTRFS_BALANCE_METADATA)

	#define BTRFS_BALANCE_FORCE (1ULL << 3)
	#define BTRFS_BALANCE_RESUME (1ULL << 4)

	/*
	* Balance filters
	*/
	#define BTRFS_BALANCE_ARGS_PROFILES (1ULL << 0)
	#define BTRFS_BALANCE_ARGS_USAGE (1ULL << 1)
	#define BTRFS_BALANCE_ARGS_DEVID (1ULL << 2)
	#define BTRFS_BALANCE_ARGS_DRANGE (1ULL << 3)
	#define BTRFS_BALANCE_ARGS_VRANGE (1ULL << 4)

	/*
	* Profile changing flags. When SOFT is set we won't relocate chunk if
	* it already has the target profile (even though it may be
	* half-filled).
	*/
	#define BTRFS_BALANCE_ARGS_CONVERT (1ULL << 8)
	#define BTRFS_BALANCE_ARGS_SOFT (1ULL << 9)

	struct btrfs_balance_args;
	struct btrfs_balance_progress;
	struct btrfs_balance_control {
	struct btrfs_fs_info *fs_info;

	struct btrfs_balance_args data;
	struct btrfs_balance_args meta;
	struct btrfs_balance_args sys;

	u64 flags;

	struct btrfs_balance_progress stat;
	};

	int btrfs_account_dev_extents_size(struct btrfs_device *device, u64 start,
	u64 end, u64 *length);

	#define btrfs_bio_size(n) (sizeof(struct btrfs_bio) + \
	(sizeof(struct btrfs_bio_stripe) * (n)))

	int btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
	u64 logical, u64 *length,
	struct btrfs_bio **bbio_ret, int mirror_num);
	int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
	u64 chunk_start, u64 physical, u64 devid,
	u64 *logical, int naddrs, int *stripe_len);
	int btrfs_read_sys_array(struct btrfs_root *root);
	int btrfs_read_chunk_tree(struct btrfs_root *root);
	int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
	struct btrfs_root *extent_root, u64 type);
	void btrfs_mapping_init(struct btrfs_mapping_tree *tree);
	void btrfs_mapping_tree_free(struct btrfs_mapping_tree *tree);
	int btrfs_map_bio(struct btrfs_root root, int rw, struct bio bio,
	int mirror_num, int async_submit);
	int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
	fmode_t flags, void *holder);
	int btrfs_scan_one_device(const char path, fmode_t flags, void holder,
	struct btrfs_fs_devices **fs_devices_ret);
	int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
	void btrfs_close_extra_devices(struct btrfs_fs_info *fs_info,
	struct btrfs_fs_devices *fs_devices, int step);
	int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
	char *device_path,
	struct btrfs_device **device);
	int btrfs_rm_device(struct btrfs_root root, char device_path);
	void btrfs_cleanup_fs_uuids(void);
	int btrfs_num_copies(struct btrfs_fs_info *fs_info, u64 logical, u64 len);
	int btrfs_grow_device(struct btrfs_trans_handle *trans,
	struct btrfs_device *device, u64 new_size);
	struct btrfs_device btrfs_find_device(struct btrfs_fs_info fs_info, u64 devid,
	u8 uuid, u8 fsid);
	int btrfs_shrink_device(struct btrfs_device *device, u64 new_size);
	int btrfs_init_new_device(struct btrfs_root root, char path);
	int btrfs_init_dev_replace_tgtdev(struct btrfs_root root, char device_path,
	struct btrfs_device **device_out);
	int btrfs_balance(struct btrfs_balance_control *bctl,
	struct btrfs_ioctl_balance_args *bargs);
	int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info);
	int btrfs_recover_balance(struct btrfs_fs_info *fs_info);
	int btrfs_pause_balance(struct btrfs_fs_info *fs_info);
	int btrfs_cancel_balance(struct btrfs_fs_info *fs_info);
	int btrfs_chunk_readonly(struct btrfs_root *root, u64 chunk_offset);
	int find_free_dev_extent(struct btrfs_device *device, u64 num_bytes,
	u64 start, u64 max_avail);
	void btrfs_dev_stat_inc_and_print(struct btrfs_device *dev, int index);
	int btrfs_get_dev_stats(struct btrfs_root *root,
	struct btrfs_ioctl_get_dev_stats *stats);
	int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info);
	int btrfs_run_dev_stats(struct btrfs_trans_handle *trans,
	struct btrfs_fs_info *fs_info);
	void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info,
	struct btrfs_device *srcdev);
	void btrfs_destroy_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
	struct btrfs_device *tgtdev);
	void btrfs_init_dev_replace_tgtdev_for_resume(struct btrfs_fs_info *fs_info,
	struct btrfs_device *tgtdev);
	int btrfs_scratch_superblock(struct btrfs_device *device);
	int btrfs_is_parity_mirror(struct btrfs_mapping_tree *map_tree,
	u64 logical, u64 len, int mirror_num);
	unsigned long btrfs_full_stripe_len(struct btrfs_root *root,
	struct btrfs_mapping_tree *map_tree,
	u64 logical);
	static inline void btrfs_dev_stat_inc(struct btrfs_device *dev,
	int index)
	{
	atomic_inc(dev->dev_stat_values + index);
	dev->dev_stats_dirty = 1;
	}

	static inline int btrfs_dev_stat_read(struct btrfs_device *dev,
	int index)
	{
	return atomic_read(dev->dev_stat_values + index);
	}

	static inline int btrfs_dev_stat_read_and_reset(struct btrfs_device *dev,
	int index)
	{
	int ret;

	ret = atomic_xchg(dev->dev_stat_values + index, 0);
	dev->dev_stats_dirty = 1;
	return ret;
	}

	static inline void btrfs_dev_stat_set(struct btrfs_device *dev,
	int index, unsigned long val)
	{
	atomic_set(dev->dev_stat_values + index, val);
	dev->dev_stats_dirty = 1;
	}

	static inline void btrfs_dev_stat_reset(struct btrfs_device *dev,
	int index)
	{
	btrfs_dev_stat_set(dev, index, 0);
	}
	#endif