/* SPDX-License-Identifier: GPL-2.0 */
/*
 * include/linux/buffer_head.h
 *
 * Everything to do with buffer_heads.
 */

#ifndef _LINUX_BUFFER_HEAD_H
#define _LINUX_BUFFER_HEAD_H

#include <linux/types.h>
#include <linux/fs.h>
#include <linux/linkage.h>
#include <linux/pagemap.h>
#include <linux/wait.h>
#include <linux/atomic.h>

#ifdef CONFIG_BLOCK

enum bh_state_bits {
        BH_Uptodate,    /* Contains valid data */
        BH_Dirty,       /* Is dirty */
        BH_Lock,        /* Is locked */
        BH_Req,         /* Has been submitted for I/O */
        BH_Uptodate_Lock,/* Used by the first bh in a page, to serialise
                          * IO completion of other buffers in the page
                          */

        BH_Mapped,      /* Has a disk mapping */
        BH_New,         /* Disk mapping was newly created by get_block */
        BH_Async_Read,  /* Is under end_buffer_async_read I/O */
        BH_Async_Write, /* Is under end_buffer_async_write I/O */
        BH_Delay,       /* Buffer is not yet allocated on disk */
        BH_Boundary,    /* Block is followed by a discontiguity */
        BH_Write_EIO,   /* I/O error on write */
        BH_Unwritten,   /* Buffer is allocated on disk but not written */
        BH_Quiet,       /* Buffer Error Prinks to be quiet */
        BH_Meta,        /* Buffer contains metadata */
        BH_Prio,        /* Buffer should be submitted with REQ_PRIO */
        BH_Defer_Completion, /* Defer AIO completion to workqueue */

        BH_PrivateStart,/* not a state bit, but the first bit available
                         * for private allocation by other entities
                         */
};

#define MAX_BUF_PER_PAGE (PAGE_SIZE / 512)

struct page;
struct buffer_head;
struct address_space;
typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);

/*
 * Historically, a buffer_head was used to map a single block
 * within a page, and of course as the unit of I/O through the
 * filesystem and block layers.  Nowadays the basic I/O unit
 * is the bio, and buffer_heads are used for extracting block
 * mappings (via a get_block_t call), for tracking state within
 * a page (via a page_mapping) and for wrapping bio submission
 * for backward compatibility reasons (e.g. submit_bh).
 */
struct buffer_head {
        unsigned long b_state;          /* buffer state bitmap (see above) */
        struct buffer_head *b_this_page;/* circular list of page's buffers */
        struct page *b_page;            /* the page this bh is mapped to */

        sector_t b_blocknr;             /* start block number */
        size_t b_size;                  /* size of mapping */
        char *b_data;                   /* pointer to data within the page */

        struct block_device *b_bdev;
        bh_end_io_t *b_end_io;          /* I/O completion */
        void *b_private;                /* reserved for b_end_io */
        struct list_head b_assoc_buffers; /* associated with another mapping */
        struct address_space *b_assoc_map;      /* mapping this buffer is
                                                   associated with */
        atomic_t b_count;               /* users using this buffer_head */
};

/*
 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
 * and buffer_foo() functions.
 * To avoid reset buffer flags that are already set, because that causes
 * a costly cache line transition, check the flag first.
 */
#define BUFFER_FNS(bit, name)                                           \
static __always_inline void set_buffer_##name(struct buffer_head *bh)   \
{                                                                       \
        if (!test_bit(BH_##bit, &(bh)->b_state))                        \
                set_bit(BH_##bit, &(bh)->b_state);                      \
}                                                                       \
static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
{                                                                       \
        clear_bit(BH_##bit, &(bh)->b_state);                            \
}                                                                       \
static __always_inline int buffer_##name(const struct buffer_head *bh)  \
{                                                                       \
        return test_bit(BH_##bit, &(bh)->b_state);                      \
}

/*
 * test_set_buffer_foo() and test_clear_buffer_foo()
 */
#define TAS_BUFFER_FNS(bit, name)                                       \
static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \
{                                                                       \
        return test_and_set_bit(BH_##bit, &(bh)->b_state);              \
}                                                                       \
static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \
{                                                                       \
        return test_and_clear_bit(BH_##bit, &(bh)->b_state);            \
}                                                                       \

/*
 * Emit the buffer bitops functions.   Note that there are also functions
 * of the form "mark_buffer_foo()".  These are higher-level functions which
 * do something in addition to setting a b_state bit.
 */
BUFFER_FNS(Uptodate, uptodate)
BUFFER_FNS(Dirty, dirty)
TAS_BUFFER_FNS(Dirty, dirty)
BUFFER_FNS(Lock, locked)
BUFFER_FNS(Req, req)
TAS_BUFFER_FNS(Req, req)
BUFFER_FNS(Mapped, mapped)
BUFFER_FNS(New, new)
BUFFER_FNS(Async_Read, async_read)
BUFFER_FNS(Async_Write, async_write)
BUFFER_FNS(Delay, delay)
BUFFER_FNS(Boundary, boundary)
BUFFER_FNS(Write_EIO, write_io_error)
BUFFER_FNS(Unwritten, unwritten)
BUFFER_FNS(Meta, meta)
BUFFER_FNS(Prio, prio)
BUFFER_FNS(Defer_Completion, defer_completion)

#define bh_offset(bh)           ((unsigned long)(bh)->b_data & ~PAGE_MASK)

/* If we *know* page->private refers to buffer_heads */
#define page_buffers(page)                                      \
        ({                                                      \
                BUG_ON(!PagePrivate(page));                     \
                ((struct buffer_head *)page_private(page));     \
        })
#define page_has_buffers(page)  PagePrivate(page)

void buffer_check_dirty_writeback(struct page *page,
                                     bool *dirty, bool *writeback);

/*
 * Declarations
 */

void mark_buffer_dirty(struct buffer_head *bh);
void mark_buffer_write_io_error(struct buffer_head *bh);
void touch_buffer(struct buffer_head *bh);
void set_bh_page(struct buffer_head *bh,
                struct page *page, unsigned long offset);
int try_to_free_buffers(struct page *);
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
                bool retry);
void create_empty_buffers(struct page *, unsigned long,
                        unsigned long b_state);
void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
void end_buffer_async_write(struct buffer_head *bh, int uptodate);

/* Things to do with buffers at mapping->private_list */
void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
int inode_has_buffers(struct inode *);
void invalidate_inode_buffers(struct inode *);
int remove_inode_buffers(struct inode *inode);
int sync_mapping_buffers(struct address_space *mapping);
void clean_bdev_aliases(struct block_device *bdev, sector_t block,
                        sector_t len);
static inline void clean_bdev_bh_alias(struct buffer_head *bh)
{
        clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1);
}

void mark_buffer_async_write(struct buffer_head *bh);
void __wait_on_buffer(struct buffer_head *);
wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
                        unsigned size);
struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block,
                                  unsigned size, gfp_t gfp);
void __brelse(struct buffer_head *);
void __bforget(struct buffer_head *);
void __breadahead(struct block_device *, sector_t block, unsigned int size);
struct buffer_head *__bread_gfp(struct block_device *,
                                sector_t block, unsigned size, gfp_t gfp);
void invalidate_bh_lrus(void);
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
void free_buffer_head(struct buffer_head * bh);
void unlock_buffer(struct buffer_head *bh);
void __lock_buffer(struct buffer_head *bh);
void ll_rw_block(int, int, int, struct buffer_head * bh[]);
int sync_dirty_buffer(struct buffer_head *bh);
int __sync_dirty_buffer(struct buffer_head *bh, int op_flags);
void write_dirty_buffer(struct buffer_head *bh, int op_flags);
int submit_bh(int, int, struct buffer_head *);
void write_boundary_block(struct block_device *bdev,
                        sector_t bblock, unsigned blocksize);
int bh_uptodate_or_lock(struct buffer_head *bh);
int bh_submit_read(struct buffer_head *bh);

extern int buffer_heads_over_limit;

/*
 * Generic address_space_operations implementations for buffer_head-backed
 * address_spaces.
 */
void block_invalidatepage(struct page *page, unsigned int offset,
                          unsigned int length);
int block_write_full_page(struct page *page, get_block_t *get_block,
                                struct writeback_control *wbc);
int __block_write_full_page(struct inode *inode, struct page *page,
                        get_block_t *get_block, struct writeback_control *wbc,
                        bh_end_io_t *handler);
int block_read_full_page(struct page*, get_block_t*);
int block_is_partially_uptodate(struct page *page, unsigned long from,
                                unsigned long count);
int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
                unsigned flags, struct page **pagep, get_block_t *get_block);
int __block_write_begin(struct page *page, loff_t pos, unsigned len,
                get_block_t *get_block);
int block_write_end(struct file *, struct address_space *,
                                loff_t, unsigned, unsigned,
                                struct page *, void *);
int generic_write_end(struct file *, struct address_space *,
                                loff_t, unsigned, unsigned,
                                struct page *, void *);
void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
void clean_page_buffers(struct page *page);
int cont_write_begin(struct file *, struct address_space *, loff_t,
                        unsigned, unsigned, struct page **, void **,
                        get_block_t *, loff_t *);
int generic_cont_expand_simple(struct inode *inode, loff_t size);
int block_commit_write(struct page *page, unsigned from, unsigned to);
int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
                                get_block_t get_block);
/* Convert errno to return value from ->page_mkwrite() call */
static inline vm_fault_t block_page_mkwrite_return(int err)
{
        if (err == 0)
                return VM_FAULT_LOCKED;
        if (err == -EFAULT || err == -EAGAIN)
                return VM_FAULT_NOPAGE;
        if (err == -ENOMEM)
                return VM_FAULT_OOM;
        /* -ENOSPC, -EDQUOT, -EIO ... */
        return VM_FAULT_SIGBUS;
}
sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
int block_truncate_page(struct address_space *, loff_t, get_block_t *);
int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned,
                                struct page **, void **, get_block_t*);
int nobh_write_end(struct file *, struct address_space *,
                                loff_t, unsigned, unsigned,
                                struct page *, void *);
int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
int nobh_writepage(struct page *page, get_block_t *get_block,
                        struct writeback_control *wbc);

void buffer_init(void);

/*
 * inline definitions
 */

static inline void attach_page_buffers(struct page *page,
                struct buffer_head *head)
{
        get_page(page);
        SetPagePrivate(page);
        set_page_private(page, (unsigned long)head);
}

static inline void get_bh(struct buffer_head *bh)
{
        atomic_inc(&bh->b_count);
}

static inline void put_bh(struct buffer_head *bh)
{
        smp_mb__before_atomic();
        atomic_dec(&bh->b_count);
}

static inline void brelse(struct buffer_head *bh)
{
        if (bh)
                __brelse(bh);
}

static inline void bforget(struct buffer_head *bh)
{
        if (bh)
                __bforget(bh);
}

static inline struct buffer_head *
sb_bread(struct super_block *sb, sector_t block)
{
        return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
}

static inline struct buffer_head *
sb_bread_unmovable(struct super_block *sb, sector_t block)
{
        return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
}

static inline void
sb_breadahead(struct super_block *sb, sector_t block)
{
        __breadahead(sb->s_bdev, block, sb->s_blocksize);
}

static inline struct buffer_head *
sb_getblk(struct super_block *sb, sector_t block)
{
        return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
}


static inline struct buffer_head *
sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
{
        return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
}

static inline struct buffer_head *
sb_find_get_block(struct super_block *sb, sector_t block)
{
        return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
}

static inline void
map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
{
        set_buffer_mapped(bh);
        bh->b_bdev = sb->s_bdev;
        bh->b_blocknr = block;
        bh->b_size = sb->s_blocksize;
}

static inline void wait_on_buffer(struct buffer_head *bh)
{
        might_sleep();
        if (buffer_locked(bh))
                __wait_on_buffer(bh);
}

static inline int trylock_buffer(struct buffer_head *bh)
{
        return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
}

static inline void lock_buffer(struct buffer_head *bh)
{
        might_sleep();
        if (!trylock_buffer(bh))
                __lock_buffer(bh);
}

static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
                                                   sector_t block,
                                                   unsigned size)
{
        return __getblk_gfp(bdev, block, size, 0);
}

static inline struct buffer_head *__getblk(struct block_device *bdev,
                                           sector_t block,
                                           unsigned size)
{
        return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
}

/**
 *  __bread() - reads a specified block and returns the bh
 *  @bdev: the block_device to read from
 *  @block: number of block
 *  @size: size (in bytes) to read
 *
 *  Reads a specified block, and returns buffer head that contains it.
 *  The page cache is allocated from movable area so that it can be migrated.
 *  It returns NULL if the block was unreadable.
 */
static inline struct buffer_head *
__bread(struct block_device *bdev, sector_t block, unsigned size)
{
        return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
}

extern int __set_page_dirty_buffers(struct page *page);

#else /* CONFIG_BLOCK */

static inline void buffer_init(void) {}
static inline int try_to_free_buffers(struct page *page) { return 1; }
static inline int inode_has_buffers(struct inode *inode) { return 0; }
static inline void invalidate_inode_buffers(struct inode *inode) {}
static inline int remove_inode_buffers(struct inode *inode) { return 1; }
static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }

#endif /* CONFIG_BLOCK */
#endif /* _LINUX_BUFFER_HEAD_H */