unsigned int need_commit_sem:1;
unsigned int skip_release_on_error:1;
};
-#define BTRFS_MAX_EXTENT_ITEM_SIZE(r) ((BTRFS_LEAF_DATA_SIZE(r) >> 4) - \
+#define BTRFS_MAX_EXTENT_ITEM_SIZE(r) ((BTRFS_LEAF_DATA_SIZE(r->fs_info) >> 4) - \
sizeof(struct btrfs_item))
struct btrfs_dev_replace {
u64 replace_state; /* see #define above */
void *cur, *orig;
struct page *page;
struct page **pages;
- struct btrfs_root *root;
+ struct btrfs_fs_info *fs_info;
struct inode *inode;
unsigned long size;
int index;
/* Used to record internally whether fs has been frozen */
int fs_frozen;
+
+ /* Cached block sizes */
+ u32 nodesize;
+ u32 sectorsize;
+ u32 stripesize;
};
+static inline struct btrfs_fs_info *btrfs_sb(struct super_block *sb)
+{
+ return sb->s_fs_info;
+}
+
struct btrfs_subvolume_writers {
struct percpu_counter counter;
wait_queue_head_t wait;
u64 objectid;
u64 last_trans;
- /* data allocations are done in sectorsize units */
- u32 sectorsize;
-
- /* node allocations are done in nodesize units */
- u32 nodesize;
-
- u32 stripesize;
-
u32 type;
u64 highest_objectid;
/* For qgroup metadata space reserve */
atomic_t qgroup_meta_rsv;
};
+static inline u32 btrfs_inode_sectorsize(const struct inode *inode)
+{
+ return btrfs_sb(inode->i_sb)->sectorsize;
+}
static inline u32 __BTRFS_LEAF_DATA_SIZE(u32 blocksize)
{
return blocksize - sizeof(struct btrfs_header);
}
-static inline u32 BTRFS_LEAF_DATA_SIZE(const struct btrfs_root *root)
+static inline u32 BTRFS_LEAF_DATA_SIZE(const struct btrfs_fs_info *info)
{
- return __BTRFS_LEAF_DATA_SIZE(root->nodesize);
+ return __BTRFS_LEAF_DATA_SIZE(info->nodesize);
}
-static inline u32 BTRFS_MAX_ITEM_SIZE(const struct btrfs_root *root)
+static inline u32 BTRFS_MAX_ITEM_SIZE(const struct btrfs_fs_info *info)
{
- return BTRFS_LEAF_DATA_SIZE(root) - sizeof(struct btrfs_item);
+ return BTRFS_LEAF_DATA_SIZE(info) - sizeof(struct btrfs_item);
}
-static inline u32 BTRFS_NODEPTRS_PER_BLOCK(const struct btrfs_root *root)
+static inline u32 BTRFS_NODEPTRS_PER_BLOCK(const struct btrfs_fs_info *info)
{
- return BTRFS_LEAF_DATA_SIZE(root) / sizeof(struct btrfs_key_ptr);
+ return BTRFS_LEAF_DATA_SIZE(info) / sizeof(struct btrfs_key_ptr);
}
#define BTRFS_FILE_EXTENT_INLINE_DATA_START \
(offsetof(struct btrfs_file_extent_item, disk_bytenr))
-static inline u32 BTRFS_MAX_INLINE_DATA_SIZE(const struct btrfs_root *root)
+static inline u32 BTRFS_MAX_INLINE_DATA_SIZE(const struct btrfs_fs_info *info)
{
- return BTRFS_MAX_ITEM_SIZE(root) -
+ return BTRFS_MAX_ITEM_SIZE(info) -
BTRFS_FILE_EXTENT_INLINE_DATA_START;
}
-static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_root *root)
+static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_fs_info *info)
{
- return BTRFS_MAX_ITEM_SIZE(root) - sizeof(struct btrfs_dir_item);
+ return BTRFS_MAX_ITEM_SIZE(info) - sizeof(struct btrfs_dir_item);
}
/*
#ifdef CONFIG_BTRFS_DEBUG
static inline int
-btrfs_should_fragment_free_space(struct btrfs_root *root,
- struct btrfs_block_group_cache *block_group)
+btrfs_should_fragment_free_space(struct btrfs_block_group_cache *block_group)
{
- return (btrfs_test_opt(root->fs_info, FRAGMENT_METADATA) &&
+ struct btrfs_fs_info *fs_info = block_group->fs_info;
+
+ return (btrfs_test_opt(fs_info, FRAGMENT_METADATA) &&
block_group->flags & BTRFS_BLOCK_GROUP_METADATA) ||
- (btrfs_test_opt(root->fs_info, FRAGMENT_DATA) &&
+ (btrfs_test_opt(fs_info, FRAGMENT_DATA) &&
block_group->flags & BTRFS_BLOCK_GROUP_DATA);
}
#endif
* this returns the address of the start of the last item,
* which is the stop of the leaf data stack
*/
-static inline unsigned int leaf_data_end(struct btrfs_root *root,
+static inline unsigned int leaf_data_end(struct btrfs_fs_info *fs_info,
struct extent_buffer *leaf)
{
u32 nr = btrfs_header_nritems(leaf);
if (nr == 0)
- return BTRFS_LEAF_DATA_SIZE(root);
+ return BTRFS_LEAF_DATA_SIZE(fs_info);
return btrfs_item_offset_nr(leaf, nr - 1);
}
BTRFS_SETGET_STACK_FUNCS(stack_dev_replace_cursor_right,
struct btrfs_dev_replace_item, cursor_right, 64);
-static inline struct btrfs_fs_info *btrfs_sb(struct super_block *sb)
-{
- return sb->s_fs_info;
-}
-
/* helper function to cast into the data area of the leaf. */
#define btrfs_item_ptr(leaf, slot, type) \
((type *)(btrfs_leaf_data(leaf) + \
/* extent-tree.c */
-u64 btrfs_csum_bytes_to_leaves(struct btrfs_root *root, u64 csum_bytes);
+u64 btrfs_csum_bytes_to_leaves(struct btrfs_fs_info *fs_info, u64 csum_bytes);
-static inline u64 btrfs_calc_trans_metadata_size(struct btrfs_root *root,
+static inline u64 btrfs_calc_trans_metadata_size(struct btrfs_fs_info *fs_info,
unsigned num_items)
{
- return root->nodesize * BTRFS_MAX_LEVEL * 2 * num_items;
+ return fs_info->nodesize * BTRFS_MAX_LEVEL * 2 * num_items;
}
/*
* Doing a truncate won't result in new nodes or leaves, just what we need for
* COW.
*/
-static inline u64 btrfs_calc_trunc_metadata_size(struct btrfs_root *root,
+static inline u64 btrfs_calc_trunc_metadata_size(struct btrfs_fs_info *fs_info,
unsigned num_items)
{
- return root->nodesize * BTRFS_MAX_LEVEL * num_items;
+ return fs_info->nodesize * BTRFS_MAX_LEVEL * num_items;
}
int btrfs_should_throttle_delayed_refs(struct btrfs_trans_handle *trans,
- struct btrfs_root *root);
+ struct btrfs_fs_info *fs_info);
int btrfs_check_space_for_delayed_refs(struct btrfs_trans_handle *trans,
- struct btrfs_root *root);
+ struct btrfs_fs_info *fs_info);
void btrfs_dec_block_group_reservations(struct btrfs_fs_info *fs_info,
const u64 start);
void btrfs_wait_block_group_reservations(struct btrfs_block_group_cache *bg);
void btrfs_wait_nocow_writers(struct btrfs_block_group_cache *bg);
void btrfs_put_block_group(struct btrfs_block_group_cache *cache);
int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
- struct btrfs_root *root, unsigned long count);
-int btrfs_async_run_delayed_refs(struct btrfs_root *root,
+ struct btrfs_fs_info *fs_info, unsigned long count);
+int btrfs_async_run_delayed_refs(struct btrfs_fs_info *fs_info,
unsigned long count, u64 transid, int wait);
-int btrfs_lookup_data_extent(struct btrfs_root *root, u64 start, u64 len);
+int btrfs_lookup_data_extent(struct btrfs_fs_info *fs_info, u64 start, u64 len);
int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
- struct btrfs_root *root, u64 bytenr,
+ struct btrfs_fs_info *fs_info, u64 bytenr,
u64 offset, int metadata, u64 *refs, u64 *flags);
-int btrfs_pin_extent(struct btrfs_root *root,
+int btrfs_pin_extent(struct btrfs_fs_info *fs_info,
u64 bytenr, u64 num, int reserved);
-int btrfs_pin_extent_for_log_replay(struct btrfs_root *root,
+int btrfs_pin_extent_for_log_replay(struct btrfs_fs_info *fs_info,
u64 bytenr, u64 num_bytes);
-int btrfs_exclude_logged_extents(struct btrfs_root *root,
+int btrfs_exclude_logged_extents(struct btrfs_fs_info *fs_info,
struct extent_buffer *eb);
int btrfs_cross_ref_exist(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct extent_buffer *buf,
u64 parent, int last_ref);
int btrfs_alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
- struct btrfs_root *root,
u64 root_objectid, u64 owner,
u64 offset, u64 ram_bytes,
struct btrfs_key *ins);
int btrfs_alloc_logged_file_extent(struct btrfs_trans_handle *trans,
- struct btrfs_root *root,
+ struct btrfs_fs_info *fs_info,
u64 root_objectid, u64 owner, u64 offset,
struct btrfs_key *ins);
int btrfs_reserve_extent(struct btrfs_root *root, u64 ram_bytes, u64 num_bytes,
int btrfs_dec_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
struct extent_buffer *buf, int full_backref);
int btrfs_set_disk_extent_flags(struct btrfs_trans_handle *trans,
- struct btrfs_root *root,
+ struct btrfs_fs_info *fs_info,
u64 bytenr, u64 num_bytes, u64 flags,
int level, int is_data);
int btrfs_free_extent(struct btrfs_trans_handle *trans,
- struct btrfs_root *root,
+ struct btrfs_fs_info *fs_info,
u64 bytenr, u64 num_bytes, u64 parent, u64 root_objectid,
u64 owner, u64 offset);
-int btrfs_free_reserved_extent(struct btrfs_root *root, u64 start, u64 len,
- int delalloc);
-int btrfs_free_and_pin_reserved_extent(struct btrfs_root *root,
+int btrfs_free_reserved_extent(struct btrfs_fs_info *fs_info,
+ u64 start, u64 len, int delalloc);
+int btrfs_free_and_pin_reserved_extent(struct btrfs_fs_info *fs_info,
u64 start, u64 len);
void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans,
- struct btrfs_root *root);
+ struct btrfs_fs_info *fs_info);
int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
- struct btrfs_root *root);
+ struct btrfs_fs_info *fs_info);
int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
- struct btrfs_root *root,
+ struct btrfs_fs_info *fs_info,
u64 bytenr, u64 num_bytes, u64 parent,
u64 root_objectid, u64 owner, u64 offset);
int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans,
- struct btrfs_root *root);
+ struct btrfs_fs_info *fs_info);
int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
- struct btrfs_root *root);
+ struct btrfs_fs_info *fs_info);
int btrfs_setup_space_cache(struct btrfs_trans_handle *trans,
- struct btrfs_root *root);
-int btrfs_extent_readonly(struct btrfs_root *root, u64 bytenr);
+ struct btrfs_fs_info *fs_info);
+int btrfs_extent_readonly(struct btrfs_fs_info *fs_info, u64 bytenr);
int btrfs_free_block_groups(struct btrfs_fs_info *info);
int btrfs_read_block_groups(struct btrfs_fs_info *info);
int btrfs_can_relocate(struct btrfs_fs_info *fs_info, u64 bytenr);
int btrfs_make_block_group(struct btrfs_trans_handle *trans,
- struct btrfs_root *root, u64 bytes_used,
+ struct btrfs_fs_info *fs_info, u64 bytes_used,
u64 type, u64 chunk_objectid, u64 chunk_offset,
u64 size);
struct btrfs_trans_handle *btrfs_start_trans_remove_block_group(
void btrfs_get_block_group_trimming(struct btrfs_block_group_cache *cache);
void btrfs_put_block_group_trimming(struct btrfs_block_group_cache *cache);
void btrfs_create_pending_block_groups(struct btrfs_trans_handle *trans,
- struct btrfs_root *root);
+ struct btrfs_fs_info *fs_info);
u64 btrfs_get_alloc_profile(struct btrfs_root *root, int data);
void btrfs_clear_space_info_full(struct btrfs_fs_info *info);
void btrfs_free_reserved_data_space_noquota(struct inode *inode, u64 start,
u64 len);
void btrfs_trans_release_metadata(struct btrfs_trans_handle *trans,
- struct btrfs_root *root);
+ struct btrfs_fs_info *fs_info);
void btrfs_trans_release_chunk_metadata(struct btrfs_trans_handle *trans);
int btrfs_orphan_reserve_metadata(struct btrfs_trans_handle *trans,
struct inode *inode);
struct btrfs_block_rsv *rsv,
int nitems,
u64 *qgroup_reserved, bool use_global_rsv);
-void btrfs_subvolume_release_metadata(struct btrfs_root *root,
+void btrfs_subvolume_release_metadata(struct btrfs_fs_info *fs_info,
struct btrfs_block_rsv *rsv,
u64 qgroup_reserved);
int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes);
int btrfs_delalloc_reserve_space(struct inode *inode, u64 start, u64 len);
void btrfs_delalloc_release_space(struct inode *inode, u64 start, u64 len);
void btrfs_init_block_rsv(struct btrfs_block_rsv *rsv, unsigned short type);
-struct btrfs_block_rsv *btrfs_alloc_block_rsv(struct btrfs_root *root,
+struct btrfs_block_rsv *btrfs_alloc_block_rsv(struct btrfs_fs_info *fs_info,
unsigned short type);
-void btrfs_free_block_rsv(struct btrfs_root *root,
+void btrfs_free_block_rsv(struct btrfs_fs_info *fs_info,
struct btrfs_block_rsv *rsv);
void __btrfs_free_block_rsv(struct btrfs_block_rsv *rsv);
int btrfs_block_rsv_add(struct btrfs_root *root,
struct btrfs_block_rsv *block_rsv, u64 num_bytes,
enum btrfs_reserve_flush_enum flush);
-int btrfs_block_rsv_check(struct btrfs_root *root,
- struct btrfs_block_rsv *block_rsv, int min_factor);
+int btrfs_block_rsv_check(struct btrfs_block_rsv *block_rsv, int min_factor);
int btrfs_block_rsv_refill(struct btrfs_root *root,
struct btrfs_block_rsv *block_rsv, u64 min_reserved,
enum btrfs_reserve_flush_enum flush);
int btrfs_cond_migrate_bytes(struct btrfs_fs_info *fs_info,
struct btrfs_block_rsv *dest, u64 num_bytes,
int min_factor);
-void btrfs_block_rsv_release(struct btrfs_root *root,
+void btrfs_block_rsv_release(struct btrfs_fs_info *fs_info,
struct btrfs_block_rsv *block_rsv,
u64 num_bytes);
int btrfs_inc_block_group_ro(struct btrfs_root *root,
struct btrfs_block_group_cache *cache);
-void btrfs_dec_block_group_ro(struct btrfs_root *root,
- struct btrfs_block_group_cache *cache);
+void btrfs_dec_block_group_ro(struct btrfs_block_group_cache *cache);
void btrfs_put_block_group_cache(struct btrfs_fs_info *info);
u64 btrfs_account_ro_block_groups_free_space(struct btrfs_space_info *sinfo);
-int btrfs_error_unpin_extent_range(struct btrfs_root *root,
+int btrfs_error_unpin_extent_range(struct btrfs_fs_info *fs_info,
u64 start, u64 end);
-int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
+int btrfs_discard_extent(struct btrfs_fs_info *fs_info, u64 bytenr,
u64 num_bytes, u64 *actual_bytes);
int btrfs_force_chunk_alloc(struct btrfs_trans_handle *trans,
- struct btrfs_root *root, u64 type);
-int btrfs_trim_fs(struct btrfs_root *root, struct fstrim_range *range);
+ struct btrfs_fs_info *fs_info, u64 type);
+int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range);
int btrfs_init_space_info(struct btrfs_fs_info *fs_info);
int btrfs_delayed_refs_qgroup_accounting(struct btrfs_trans_handle *trans,
void btrfs_end_write_no_snapshoting(struct btrfs_root *root);
void btrfs_wait_for_snapshot_creation(struct btrfs_root *root);
void check_system_chunk(struct btrfs_trans_handle *trans,
- struct btrfs_root *root,
- const u64 type);
+ struct btrfs_fs_info *fs_info, const u64 type);
u64 add_new_free_space(struct btrfs_block_group_cache *block_group,
struct btrfs_fs_info *info, u64 start, u64 end);
struct extent_buffer **cow_ret, u64 new_root_objectid);
int btrfs_block_can_be_shared(struct btrfs_root *root,
struct extent_buffer *buf);
-void btrfs_extend_item(struct btrfs_root *root, struct btrfs_path *path,
+void btrfs_extend_item(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
u32 data_size);
-void btrfs_truncate_item(struct btrfs_root *root, struct btrfs_path *path,
- u32 new_size, int from_end);
+void btrfs_truncate_item(struct btrfs_fs_info *fs_info,
+ struct btrfs_path *path, u32 new_size, int from_end);
int btrfs_split_item(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_path *path,
{
return btrfs_next_old_item(root, p, 0);
}
-int btrfs_leaf_free_space(struct btrfs_root *root, struct extent_buffer *leaf);
+int btrfs_leaf_free_space(struct btrfs_fs_info *fs_info,
+ struct extent_buffer *leaf);
int __must_check btrfs_drop_snapshot(struct btrfs_root *root,
struct btrfs_block_rsv *block_rsv,
int update_ref, int for_reloc);
* anything except sleeping. This function is used to check the status of
* the fs.
*/
-static inline int btrfs_need_cleaner_sleep(struct btrfs_root *root)
+static inline int btrfs_need_cleaner_sleep(struct btrfs_fs_info *fs_info)
{
- return (root->fs_info->sb->s_flags & MS_RDONLY ||
- btrfs_fs_closing(root->fs_info));
+ return fs_info->sb->s_flags & MS_RDONLY || btrfs_fs_closing(fs_info);
}
static inline void free_fs_info(struct btrfs_fs_info *fs_info)
struct btrfs_path *path, u64 dir,
const char *name, u16 name_len,
int mod);
-int verify_dir_item(struct btrfs_root *root,
+int verify_dir_item(struct btrfs_fs_info *fs_info,
struct extent_buffer *leaf,
struct btrfs_dir_item *dir_item);
-struct btrfs_dir_item *btrfs_match_dir_item_name(struct btrfs_root *root,
+struct btrfs_dir_item *btrfs_match_dir_item_name(struct btrfs_fs_info *fs_info,
struct btrfs_path *path,
const char *name,
int name_len);
struct btrfs_dio_private;
int btrfs_del_csums(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytenr, u64 len);
-int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
- struct bio *bio, u32 *dst);
-int btrfs_lookup_bio_sums_dio(struct btrfs_root *root, struct inode *inode,
- struct bio *bio, u64 logical_offset);
+int btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, u32 *dst);
+int btrfs_lookup_bio_sums_dio(struct inode *inode, struct bio *bio,
+ u64 logical_offset);
int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
u64 objectid, u64 pos,
int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_ordered_sum *sums);
-int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
- struct bio *bio, u64 file_start, int contig);
+int btrfs_csum_one_bio(struct inode *inode, struct bio *bio,
+ u64 file_start, int contig);
int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
struct list_head *list, int search_commit);
void btrfs_extent_item_to_extent_map(struct inode *inode,
int btrfs_cont_expand(struct inode *inode, loff_t oldsize, loff_t size);
void btrfs_invalidate_inodes(struct btrfs_root *root);
void btrfs_add_delayed_iput(struct inode *inode);
-void btrfs_run_delayed_iputs(struct btrfs_root *root);
+void btrfs_run_delayed_iputs(struct btrfs_fs_info *fs_info);
int btrfs_prealloc_file_range(struct inode *inode, int mode,
u64 start, u64 num_bytes, u64 min_size,
loff_t actual_len, u64 *alloc_hint);
int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
struct inode *inode, u64 start, u64 end);
int btrfs_release_file(struct inode *inode, struct file *file);
-int btrfs_dirty_pages(struct btrfs_root *root, struct inode *inode,
- struct page **pages, size_t num_pages,
- loff_t pos, size_t write_bytes,
+int btrfs_dirty_pages(struct inode *inode, struct page **pages,
+ size_t num_pages, loff_t pos, size_t write_bytes,
struct extent_state **cached);
int btrfs_fdatawrite_range(struct inode *inode, loff_t start, loff_t end);
-ssize_t btrfs_copy_file_range(struct file *file_in, loff_t pos_in,
- struct file *file_out, loff_t pos_out,
- size_t len, unsigned int flags);
int btrfs_clone_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out, u64 len);
ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size);
/* super.c */
-int btrfs_parse_options(struct btrfs_root *root, char *options,
+int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
unsigned long new_flags);
int btrfs_sync_fs(struct super_block *sb, int wait);
/* Report first abort since mount */ \
if (!test_and_set_bit(BTRFS_FS_STATE_TRANS_ABORTED, \
&((trans)->fs_info->fs_state))) { \
- WARN(1, KERN_DEBUG \
- "BTRFS: Transaction aborted (error %d)\n", \
- (errno)); \
+ if ((errno) != -EIO) { \
+ WARN(1, KERN_DEBUG \
+ "BTRFS: Transaction aborted (error %d)\n", \
+ (errno)); \
+ } else { \
+ pr_debug("BTRFS: Transaction aborted (error %d)\n", \
+ (errno)); \
+ } \
} \
__btrfs_abort_transaction((trans), __func__, \
__LINE__, (errno)); \
int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
u64 end, struct btrfs_scrub_progress *progress,
int readonly, int is_dev_replace);
-void btrfs_scrub_pause(struct btrfs_root *root);
-void btrfs_scrub_continue(struct btrfs_root *root);
+void btrfs_scrub_pause(struct btrfs_fs_info *fs_info);
+void btrfs_scrub_continue(struct btrfs_fs_info *fs_info);
int btrfs_scrub_cancel(struct btrfs_fs_info *info);
int btrfs_scrub_cancel_dev(struct btrfs_fs_info *info,
struct btrfs_device *dev);
-int btrfs_scrub_progress(struct btrfs_root *root, u64 devid,
+int btrfs_scrub_progress(struct btrfs_fs_info *fs_info, u64 devid,
struct btrfs_scrub_progress *progress);
/* dev-replace.c */
/* reada.c */
struct reada_control {
- struct btrfs_root *root; /* tree to prefetch */
+ struct btrfs_fs_info *fs_info; /* tree to prefetch */
struct btrfs_key key_start;
struct btrfs_key key_end; /* exclusive */
atomic_t elems;