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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef BTRFS_SUBPAGE_H
#define BTRFS_SUBPAGE_H
#include <linux/spinlock.h>
/*
* Maximum page size we support is 64K, minimum sector size is 4K, u16 bitmap
* is sufficient. Regular bitmap_* is not used due to size reasons.
*/
#define BTRFS_SUBPAGE_BITMAP_SIZE 16
/*
* Structure to trace status of each sector inside a page, attached to
* page::private for both data and metadata inodes.
*/
struct btrfs_subpage {
/* Common members for both data and metadata pages */
spinlock_t lock;
union {
/*
* Structures only used by metadata
*
* @eb_refs should only be operated under private_lock, as it
* manages whether the subpage can be detached.
*/
atomic_t eb_refs;
/* Structures only used by data */
};
};
enum btrfs_subpage_type {
BTRFS_SUBPAGE_METADATA,
BTRFS_SUBPAGE_DATA,
};
int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
struct page *page, enum btrfs_subpage_type type);
void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info,
struct page *page);
/* Allocate additional data where page represents more than one sector */
int btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
struct btrfs_subpage **ret,
enum btrfs_subpage_type type);
void btrfs_free_subpage(struct btrfs_subpage *subpage);
void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info,
struct page *page);
void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,
struct page *page);
#endif
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