/* 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/blk_types.h> #include <linux/fs.h> #include <linux/linkage.h> #include <linux/pagemap.h> #include <linux/wait.h> #include <linux/atomic.h> enum bh_state_bits { … }; #define MAX_BUF_PER_PAGE … struct page; struct buffer_head; struct address_space; bh_end_io_t; /* * 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 folio (via a folio_mapping) and for wrapping bio submission * for backward compatibility reasons (e.g. submit_bh). */ struct 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) … /* * test_set_buffer_foo() and test_clear_buffer_foo() */ #define TAS_BUFFER_FNS(bit, name) … \ /* * 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(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) static __always_inline void set_buffer_uptodate(struct buffer_head *bh) { … } static __always_inline void clear_buffer_uptodate(struct buffer_head *bh) { … } static __always_inline int buffer_uptodate(const struct buffer_head *bh) { … } static inline unsigned long bh_offset(const struct buffer_head *bh) { … } /* If we *know* page->private refers to buffer_heads */ #define page_buffers(page) … #define page_has_buffers(page) … #define folio_buffers(folio) … void buffer_check_dirty_writeback(struct folio *folio, 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 folio_set_bh(struct buffer_head *bh, struct folio *folio, unsigned long offset); struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size, gfp_t gfp); struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size); struct buffer_head *create_empty_buffers(struct folio *folio, unsigned long blocksize, 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); /* Things to do with buffers at mapping->private_list */ void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end, bool datasync); int generic_buffers_fsync(struct file *file, loff_t start, loff_t end, bool datasync); 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) { … } 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 *bdev_getblk(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); 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); int sync_dirty_buffer(struct buffer_head *bh); int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags); void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags); void submit_bh(blk_opf_t, 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_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait); void __bh_read_batch(int nr, struct buffer_head *bhs[], blk_opf_t op_flags, bool force_lock); /* * Generic address_space_operations implementations for buffer_head-backed * address_spaces. */ void block_invalidate_folio(struct folio *folio, size_t offset, size_t length); int block_write_full_folio(struct folio *folio, struct writeback_control *wbc, void *get_block); int __block_write_full_folio(struct inode *inode, struct folio *folio, get_block_t *get_block, struct writeback_control *wbc); int block_read_full_folio(struct folio *, get_block_t *); bool block_is_partially_uptodate(struct folio *, size_t from, size_t count); int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, struct folio **foliop, get_block_t *get_block); int __block_write_begin(struct folio *folio, loff_t pos, unsigned len, get_block_t *get_block); int block_write_end(struct file *, struct address_space *, loff_t, unsigned len, unsigned copied, struct folio *, void *); int generic_write_end(struct file *, struct address_space *, loff_t, unsigned len, unsigned copied, struct folio *, void *); void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to); int cont_write_begin(struct file *, struct address_space *, loff_t, unsigned, struct folio **, void **, get_block_t *, loff_t *); int generic_cont_expand_simple(struct inode *inode, loff_t size); void block_commit_write(struct page *page, unsigned int from, unsigned int to); int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, get_block_t get_block); 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 *); #ifdef CONFIG_MIGRATION extern int buffer_migrate_folio(struct address_space *, struct folio *dst, struct folio *src, enum migrate_mode); extern int buffer_migrate_folio_norefs(struct address_space *, struct folio *dst, struct folio *src, enum migrate_mode); #else #define buffer_migrate_folio … #define buffer_migrate_folio_norefs … #endif /* * inline definitions */ static inline void get_bh(struct buffer_head *bh) { … } static inline void put_bh(struct buffer_head *bh) { … } /** * brelse - Release a buffer. * @bh: The buffer to release. * * Decrement a buffer_head's reference count. If @bh is NULL, this * function is a no-op. * * If all buffers on a folio have zero reference count, are clean * and unlocked, and if the folio is unlocked and not under writeback * then try_to_free_buffers() may strip the buffers from the folio in * preparation for freeing it (sometimes, rarely, buffers are removed * from a folio but it ends up not being freed, and buffers may later * be reattached). * * Context: Any context. */ static inline void brelse(struct buffer_head *bh) { … } /** * bforget - Discard any dirty data in a buffer. * @bh: The buffer to forget. * * Call this function instead of brelse() if the data written to a buffer * no longer needs to be written back. It will clear the buffer's dirty * flag so writeback of this buffer will be skipped. * * Context: Any context. */ static inline void bforget(struct buffer_head *bh) { … } static inline struct buffer_head * sb_bread(struct super_block *sb, sector_t block) { … } static inline struct buffer_head * sb_bread_unmovable(struct super_block *sb, sector_t block) { … } static inline void sb_breadahead(struct super_block *sb, sector_t block) { … } static inline struct buffer_head *getblk_unmovable(struct block_device *bdev, sector_t block, unsigned size) { … } static inline struct buffer_head *__getblk(struct block_device *bdev, sector_t block, unsigned size) { … } static inline struct buffer_head *sb_getblk(struct super_block *sb, sector_t block) { … } static inline struct buffer_head *sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp) { … } static inline struct buffer_head * sb_find_get_block(struct super_block *sb, sector_t block) { … } static inline void map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) { … } static inline void wait_on_buffer(struct buffer_head *bh) { … } static inline int trylock_buffer(struct buffer_head *bh) { … } static inline void lock_buffer(struct buffer_head *bh) { … } static inline void bh_readahead(struct buffer_head *bh, blk_opf_t op_flags) { … } static inline void bh_read_nowait(struct buffer_head *bh, blk_opf_t op_flags) { … } /* Returns 1 if buffer uptodated, 0 on success, and -EIO on error. */ static inline int bh_read(struct buffer_head *bh, blk_opf_t op_flags) { … } static inline void bh_read_batch(int nr, struct buffer_head *bhs[]) { … } static inline void bh_readahead_batch(int nr, struct buffer_head *bhs[], blk_opf_t op_flags) { … } /** * __bread() - Read a block. * @bdev: The block device to read from. * @block: Block number in units of block size. * @size: The block size of this device in bytes. * * Read a specified block, and return the buffer head that refers * to it. The memory is allocated from the movable area so that it can * be migrated. The returned buffer head has its refcount increased. * The caller should call brelse() when it has finished with the buffer. * * Context: May sleep waiting for I/O. * Return: NULL if the block was unreadable. */ static inline struct buffer_head *__bread(struct block_device *bdev, sector_t block, unsigned size) { … } /** * get_nth_bh - Get a reference on the n'th buffer after this one. * @bh: The buffer to start counting from. * @count: How many buffers to skip. * * This is primarily useful for finding the nth buffer in a folio; in * that case you pass the head buffer and the byte offset in the folio * divided by the block size. It can be used for other purposes, but * it will wrap at the end of the folio rather than returning NULL or * proceeding to the next folio for you. * * Return: The requested buffer with an elevated refcount. */ static inline __must_check struct buffer_head *get_nth_bh(struct buffer_head *bh, unsigned int count) { … } bool block_dirty_folio(struct address_space *mapping, struct folio *folio); #ifdef CONFIG_BUFFER_HEAD void buffer_init(void); bool try_to_free_buffers(struct folio *folio); int inode_has_buffers(struct inode *inode); void invalidate_inode_buffers(struct inode *inode); int remove_inode_buffers(struct inode *inode); int sync_mapping_buffers(struct address_space *mapping); void invalidate_bh_lrus(void); void invalidate_bh_lrus_cpu(void); bool has_bh_in_lru(int cpu, void *dummy); extern int buffer_heads_over_limit; #else /* CONFIG_BUFFER_HEAD */ static inline void buffer_init(void) {} static inline bool try_to_free_buffers(struct folio *folio) { return true; } 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; } static inline void invalidate_bh_lrus(void) {} static inline void invalidate_bh_lrus_cpu(void) {} static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; } #define buffer_heads_over_limit … #endif /* CONFIG_BUFFER_HEAD */ #endif /* _LINUX_BUFFER_HEAD_H */
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