linux/fs/libfs.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *	fs/libfs.c
 *	Library for filesystems writers.
 */

#include <linux/blkdev.h>
#include <linux/export.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <linux/quotaops.h>
#include <linux/mutex.h>
#include <linux/namei.h>
#include <linux/exportfs.h>
#include <linux/iversion.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h> /* sync_mapping_buffers */
#include <linux/fs_context.h>
#include <linux/pseudo_fs.h>
#include <linux/fsnotify.h>
#include <linux/unicode.h>
#include <linux/fscrypt.h>
#include <linux/pidfs.h>

#include <linux/uaccess.h>

#include "internal.h"

int simple_getattr(struct mnt_idmap *idmap, const struct path *path,
		   struct kstat *stat, u32 request_mask,
		   unsigned int query_flags)
{ … }
EXPORT_SYMBOL(…);

int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
{ … }
EXPORT_SYMBOL(…);

/*
 * Retaining negative dentries for an in-memory filesystem just wastes
 * memory and lookup time: arrange for them to be deleted immediately.
 */
int always_delete_dentry(const struct dentry *dentry)
{ … }
EXPORT_SYMBOL(…);

const struct dentry_operations simple_dentry_operations = …;
EXPORT_SYMBOL(…);

/*
 * Lookup the data. This is trivial - if the dentry didn't already
 * exist, we know it is negative.  Set d_op to delete negative dentries.
 */
struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{ … }
EXPORT_SYMBOL(…);

int dcache_dir_open(struct inode *inode, struct file *file)
{ … }
EXPORT_SYMBOL(…);

int dcache_dir_close(struct inode *inode, struct file *file)
{ … }
EXPORT_SYMBOL(…);

/* parent is locked at least shared */
/*
 * Returns an element of siblings' list.
 * We are looking for <count>th positive after <p>; if
 * found, dentry is grabbed and returned to caller.
 * If no such element exists, NULL is returned.
 */
static struct dentry *scan_positives(struct dentry *cursor,
					struct hlist_node **p,
					loff_t count,
					struct dentry *last)
{ … }

loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
{ … }
EXPORT_SYMBOL(…);

/*
 * Directory is locked and all positive dentries in it are safe, since
 * for ramfs-type trees they can't go away without unlink() or rmdir(),
 * both impossible due to the lock on directory.
 */

int dcache_readdir(struct file *file, struct dir_context *ctx)
{ … }
EXPORT_SYMBOL(…);

ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
{ … }
EXPORT_SYMBOL(…);

const struct file_operations simple_dir_operations = …;
EXPORT_SYMBOL(…);

const struct inode_operations simple_dir_inode_operations = …;
EXPORT_SYMBOL(…);

/* 0 is '.', 1 is '..', so always start with offset 2 or more */
enum { … };

static void offset_set(struct dentry *dentry, long offset)
{ … }

static long dentry2offset(struct dentry *dentry)
{ … }

static struct lock_class_key simple_offset_lock_class;

/**
 * simple_offset_init - initialize an offset_ctx
 * @octx: directory offset map to be initialized
 *
 */
void simple_offset_init(struct offset_ctx *octx)
{ … }

/**
 * simple_offset_add - Add an entry to a directory's offset map
 * @octx: directory offset ctx to be updated
 * @dentry: new dentry being added
 *
 * Returns zero on success. @octx and the dentry's offset are updated.
 * Otherwise, a negative errno value is returned.
 */
int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry)
{ … }

static int simple_offset_replace(struct offset_ctx *octx, struct dentry *dentry,
				 long offset)
{ … }

/**
 * simple_offset_remove - Remove an entry to a directory's offset map
 * @octx: directory offset ctx to be updated
 * @dentry: dentry being removed
 *
 */
void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry)
{ … }

/**
 * simple_offset_empty - Check if a dentry can be unlinked
 * @dentry: dentry to be tested
 *
 * Returns 0 if @dentry is a non-empty directory; otherwise returns 1.
 */
int simple_offset_empty(struct dentry *dentry)
{ … }

/**
 * simple_offset_rename - handle directory offsets for rename
 * @old_dir: parent directory of source entry
 * @old_dentry: dentry of source entry
 * @new_dir: parent_directory of destination entry
 * @new_dentry: dentry of destination
 *
 * Caller provides appropriate serialization.
 *
 * User space expects the directory offset value of the replaced
 * (new) directory entry to be unchanged after a rename.
 *
 * Returns zero on success, a negative errno value on failure.
 */
int simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry,
			 struct inode *new_dir, struct dentry *new_dentry)
{ … }

/**
 * simple_offset_rename_exchange - exchange rename with directory offsets
 * @old_dir: parent of dentry being moved
 * @old_dentry: dentry being moved
 * @new_dir: destination parent
 * @new_dentry: destination dentry
 *
 * This API preserves the directory offset values. Caller provides
 * appropriate serialization.
 *
 * Returns zero on success. Otherwise a negative errno is returned and the
 * rename is rolled back.
 */
int simple_offset_rename_exchange(struct inode *old_dir,
				  struct dentry *old_dentry,
				  struct inode *new_dir,
				  struct dentry *new_dentry)
{ … }

/**
 * simple_offset_destroy - Release offset map
 * @octx: directory offset ctx that is about to be destroyed
 *
 * During fs teardown (eg. umount), a directory's offset map might still
 * contain entries. xa_destroy() cleans out anything that remains.
 */
void simple_offset_destroy(struct offset_ctx *octx)
{ … }

/**
 * offset_dir_llseek - Advance the read position of a directory descriptor
 * @file: an open directory whose position is to be updated
 * @offset: a byte offset
 * @whence: enumerator describing the starting position for this update
 *
 * SEEK_END, SEEK_DATA, and SEEK_HOLE are not supported for directories.
 *
 * Returns the updated read position if successful; otherwise a
 * negative errno is returned and the read position remains unchanged.
 */
static loff_t offset_dir_llseek(struct file *file, loff_t offset, int whence)
{ … }

static struct dentry *offset_find_next(struct offset_ctx *octx, loff_t offset)
{ … }

static bool offset_dir_emit(struct dir_context *ctx, struct dentry *dentry)
{ … }

static void *offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
{ … }

/**
 * offset_readdir - Emit entries starting at offset @ctx->pos
 * @file: an open directory to iterate over
 * @ctx: directory iteration context
 *
 * Caller must hold @file's i_rwsem to prevent insertion or removal of
 * entries during this call.
 *
 * On entry, @ctx->pos contains an offset that represents the first entry
 * to be read from the directory.
 *
 * The operation continues until there are no more entries to read, or
 * until the ctx->actor indicates there is no more space in the caller's
 * output buffer.
 *
 * On return, @ctx->pos contains an offset that will read the next entry
 * in this directory when offset_readdir() is called again with @ctx.
 *
 * Return values:
 *   %0 - Complete
 */
static int offset_readdir(struct file *file, struct dir_context *ctx)
{ … }

const struct file_operations simple_offset_dir_operations = …;

static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
{ … }

void simple_recursive_removal(struct dentry *dentry,
                              void (*callback)(struct dentry *))
{ … }
EXPORT_SYMBOL(…);

static const struct super_operations simple_super_operations = …;

static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
{ … }

static int pseudo_fs_get_tree(struct fs_context *fc)
{ … }

static void pseudo_fs_free(struct fs_context *fc)
{ … }

static const struct fs_context_operations pseudo_fs_context_ops = …;

/*
 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 * will never be mountable)
 */
struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
					unsigned long magic)
{ … }
EXPORT_SYMBOL(…);

int simple_open(struct inode *inode, struct file *file)
{ … }
EXPORT_SYMBOL(…);

int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
{ … }
EXPORT_SYMBOL(…);

int simple_empty(struct dentry *dentry)
{ … }
EXPORT_SYMBOL(…);

int simple_unlink(struct inode *dir, struct dentry *dentry)
{ … }
EXPORT_SYMBOL(…);

int simple_rmdir(struct inode *dir, struct dentry *dentry)
{ … }
EXPORT_SYMBOL(…);

/**
 * simple_rename_timestamp - update the various inode timestamps for rename
 * @old_dir: old parent directory
 * @old_dentry: dentry that is being renamed
 * @new_dir: new parent directory
 * @new_dentry: target for rename
 *
 * POSIX mandates that the old and new parent directories have their ctime and
 * mtime updated, and that inodes of @old_dentry and @new_dentry (if any), have
 * their ctime updated.
 */
void simple_rename_timestamp(struct inode *old_dir, struct dentry *old_dentry,
			     struct inode *new_dir, struct dentry *new_dentry)
{ … }
EXPORT_SYMBOL_GPL(…);

int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
			   struct inode *new_dir, struct dentry *new_dentry)
{ … }
EXPORT_SYMBOL_GPL(…);

int simple_rename(struct mnt_idmap *idmap, struct inode *old_dir,
		  struct dentry *old_dentry, struct inode *new_dir,
		  struct dentry *new_dentry, unsigned int flags)
{ … }
EXPORT_SYMBOL(…);

/**
 * simple_setattr - setattr for simple filesystem
 * @idmap: idmap of the target mount
 * @dentry: dentry
 * @iattr: iattr structure
 *
 * Returns 0 on success, -error on failure.
 *
 * simple_setattr is a simple ->setattr implementation without a proper
 * implementation of size changes.
 *
 * It can either be used for in-memory filesystems or special files
 * on simple regular filesystems.  Anything that needs to change on-disk
 * or wire state on size changes needs its own setattr method.
 */
int simple_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
		   struct iattr *iattr)
{ … }
EXPORT_SYMBOL(…);

static int simple_read_folio(struct file *file, struct folio *folio)
{ … }

int simple_write_begin(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len,
			struct page **pagep, void **fsdata)
{ … }
EXPORT_SYMBOL(…);

/**
 * simple_write_end - .write_end helper for non-block-device FSes
 * @file: See .write_end of address_space_operations
 * @mapping: 		"
 * @pos: 		"
 * @len: 		"
 * @copied: 		"
 * @page: 		"
 * @fsdata: 		"
 *
 * simple_write_end does the minimum needed for updating a page after writing is
 * done. It has the same API signature as the .write_end of
 * address_space_operations vector. So it can just be set onto .write_end for
 * FSes that don't need any other processing. i_mutex is assumed to be held.
 * Block based filesystems should use generic_write_end().
 * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
 * is not called, so a filesystem that actually does store data in .write_inode
 * should extend on what's done here with a call to mark_inode_dirty() in the
 * case that i_size has changed.
 *
 * Use *ONLY* with simple_read_folio()
 */
static int simple_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{ … }

/*
 * Provides ramfs-style behavior: data in the pagecache, but no writeback.
 */
const struct address_space_operations ram_aops = …;
EXPORT_SYMBOL(…);

/*
 * the inodes created here are not hashed. If you use iunique to generate
 * unique inode values later for this filesystem, then you must take care
 * to pass it an appropriate max_reserved value to avoid collisions.
 */
int simple_fill_super(struct super_block *s, unsigned long magic,
		      const struct tree_descr *files)
{ … }
EXPORT_SYMBOL(…);

static DEFINE_SPINLOCK(pin_fs_lock);

int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
{ … }
EXPORT_SYMBOL(…);

void simple_release_fs(struct vfsmount **mount, int *count)
{ … }
EXPORT_SYMBOL(…);

/**
 * simple_read_from_buffer - copy data from the buffer to user space
 * @to: the user space buffer to read to
 * @count: the maximum number of bytes to read
 * @ppos: the current position in the buffer
 * @from: the buffer to read from
 * @available: the size of the buffer
 *
 * The simple_read_from_buffer() function reads up to @count bytes from the
 * buffer @from at offset @ppos into the user space address starting at @to.
 *
 * On success, the number of bytes read is returned and the offset @ppos is
 * advanced by this number, or negative value is returned on error.
 **/
ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
				const void *from, size_t available)
{ … }
EXPORT_SYMBOL(…);

/**
 * simple_write_to_buffer - copy data from user space to the buffer
 * @to: the buffer to write to
 * @available: the size of the buffer
 * @ppos: the current position in the buffer
 * @from: the user space buffer to read from
 * @count: the maximum number of bytes to read
 *
 * The simple_write_to_buffer() function reads up to @count bytes from the user
 * space address starting at @from into the buffer @to at offset @ppos.
 *
 * On success, the number of bytes written is returned and the offset @ppos is
 * advanced by this number, or negative value is returned on error.
 **/
ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
		const void __user *from, size_t count)
{ … }
EXPORT_SYMBOL(…);

/**
 * memory_read_from_buffer - copy data from the buffer
 * @to: the kernel space buffer to read to
 * @count: the maximum number of bytes to read
 * @ppos: the current position in the buffer
 * @from: the buffer to read from
 * @available: the size of the buffer
 *
 * The memory_read_from_buffer() function reads up to @count bytes from the
 * buffer @from at offset @ppos into the kernel space address starting at @to.
 *
 * On success, the number of bytes read is returned and the offset @ppos is
 * advanced by this number, or negative value is returned on error.
 **/
ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
				const void *from, size_t available)
{ … }
EXPORT_SYMBOL(…);

/*
 * Transaction based IO.
 * The file expects a single write which triggers the transaction, and then
 * possibly a read which collects the result - which is stored in a
 * file-local buffer.
 */

void simple_transaction_set(struct file *file, size_t n)
{ … }
EXPORT_SYMBOL(…);

char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
{ … }
EXPORT_SYMBOL(…);

ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
{ … }
EXPORT_SYMBOL(…);

int simple_transaction_release(struct inode *inode, struct file *file)
{ … }
EXPORT_SYMBOL(…);

/* Simple attribute files */

struct simple_attr { … };

/* simple_attr_open is called by an actual attribute open file operation
 * to set the attribute specific access operations. */
int simple_attr_open(struct inode *inode, struct file *file,
		     int (*get)(void *, u64 *), int (*set)(void *, u64),
		     const char *fmt)
{ … }
EXPORT_SYMBOL_GPL(…);

int simple_attr_release(struct inode *inode, struct file *file)
{ … }
EXPORT_SYMBOL_GPL(…);	/* GPL-only?  This?  Really? */

/* read from the buffer that is filled with the get function */
ssize_t simple_attr_read(struct file *file, char __user *buf,
			 size_t len, loff_t *ppos)
{ … }
EXPORT_SYMBOL_GPL(…);

/* interpret the buffer as a number to call the set function with */
static ssize_t simple_attr_write_xsigned(struct file *file, const char __user *buf,
			  size_t len, loff_t *ppos, bool is_signed)
{ … }

ssize_t simple_attr_write(struct file *file, const char __user *buf,
			  size_t len, loff_t *ppos)
{ … }
EXPORT_SYMBOL_GPL(…);

ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
			  size_t len, loff_t *ppos)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * generic_encode_ino32_fh - generic export_operations->encode_fh function
 * @inode:   the object to encode
 * @fh:      where to store the file handle fragment
 * @max_len: maximum length to store there (in 4 byte units)
 * @parent:  parent directory inode, if wanted
 *
 * This generic encode_fh function assumes that the 32 inode number
 * is suitable for locating an inode, and that the generation number
 * can be used to check that it is still valid.  It places them in the
 * filehandle fragment where export_decode_fh expects to find them.
 */
int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
			    struct inode *parent)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
 * @sb:		filesystem to do the file handle conversion on
 * @fid:	file handle to convert
 * @fh_len:	length of the file handle in bytes
 * @fh_type:	type of file handle
 * @get_inode:	filesystem callback to retrieve inode
 *
 * This function decodes @fid as long as it has one of the well-known
 * Linux filehandle types and calls @get_inode on it to retrieve the
 * inode for the object specified in the file handle.
 */
struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
		int fh_len, int fh_type, struct inode *(*get_inode)
			(struct super_block *sb, u64 ino, u32 gen))
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * generic_fh_to_parent - generic helper for the fh_to_parent export operation
 * @sb:		filesystem to do the file handle conversion on
 * @fid:	file handle to convert
 * @fh_len:	length of the file handle in bytes
 * @fh_type:	type of file handle
 * @get_inode:	filesystem callback to retrieve inode
 *
 * This function decodes @fid as long as it has one of the well-known
 * Linux filehandle types and calls @get_inode on it to retrieve the
 * inode for the _parent_ object specified in the file handle if it
 * is specified in the file handle, or NULL otherwise.
 */
struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
		int fh_len, int fh_type, struct inode *(*get_inode)
			(struct super_block *sb, u64 ino, u32 gen))
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * __generic_file_fsync - generic fsync implementation for simple filesystems
 *
 * @file:	file to synchronize
 * @start:	start offset in bytes
 * @end:	end offset in bytes (inclusive)
 * @datasync:	only synchronize essential metadata if true
 *
 * This is a generic implementation of the fsync method for simple
 * filesystems which track all non-inode metadata in the buffers list
 * hanging off the address_space structure.
 */
int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
				 int datasync)
{ … }
EXPORT_SYMBOL(…);

/**
 * generic_file_fsync - generic fsync implementation for simple filesystems
 *			with flush
 * @file:	file to synchronize
 * @start:	start offset in bytes
 * @end:	end offset in bytes (inclusive)
 * @datasync:	only synchronize essential metadata if true
 *
 */

int generic_file_fsync(struct file *file, loff_t start, loff_t end,
		       int datasync)
{ … }
EXPORT_SYMBOL(…);

/**
 * generic_check_addressable - Check addressability of file system
 * @blocksize_bits:	log of file system block size
 * @num_blocks:		number of blocks in file system
 *
 * Determine whether a file system with @num_blocks blocks (and a
 * block size of 2**@blocksize_bits) is addressable by the sector_t
 * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
 */
int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
{ … }
EXPORT_SYMBOL(…);

/*
 * No-op implementation of ->fsync for in-memory filesystems.
 */
int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{ … }
EXPORT_SYMBOL(…);

ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{ … }
EXPORT_SYMBOL_GPL(…);

/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
void kfree_link(void *p)
{ … }
EXPORT_SYMBOL(…);

struct inode *alloc_anon_inode(struct super_block *s)
{ … }
EXPORT_SYMBOL(…);

/**
 * simple_nosetlease - generic helper for prohibiting leases
 * @filp: file pointer
 * @arg: type of lease to obtain
 * @flp: new lease supplied for insertion
 * @priv: private data for lm_setup operation
 *
 * Generic helper for filesystems that do not wish to allow leases to be set.
 * All arguments are ignored and it just returns -EINVAL.
 */
int
simple_nosetlease(struct file *filp, int arg, struct file_lease **flp,
		  void **priv)
{ … }
EXPORT_SYMBOL(…);

/**
 * simple_get_link - generic helper to get the target of "fast" symlinks
 * @dentry: not used here
 * @inode: the symlink inode
 * @done: not used here
 *
 * Generic helper for filesystems to use for symlink inodes where a pointer to
 * the symlink target is stored in ->i_link.  NOTE: this isn't normally called,
 * since as an optimization the path lookup code uses any non-NULL ->i_link
 * directly, without calling ->get_link().  But ->get_link() still must be set,
 * to mark the inode_operations as being for a symlink.
 *
 * Return: the symlink target
 */
const char *simple_get_link(struct dentry *dentry, struct inode *inode,
			    struct delayed_call *done)
{ … }
EXPORT_SYMBOL(…);

const struct inode_operations simple_symlink_inode_operations = …;
EXPORT_SYMBOL(…);

/*
 * Operations for a permanently empty directory.
 */
static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{ … }

static int empty_dir_getattr(struct mnt_idmap *idmap,
			     const struct path *path, struct kstat *stat,
			     u32 request_mask, unsigned int query_flags)
{ … }

static int empty_dir_setattr(struct mnt_idmap *idmap,
			     struct dentry *dentry, struct iattr *attr)
{ … }

static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
{ … }

static const struct inode_operations empty_dir_inode_operations = …;

static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
{ … }

static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
{ … }

static const struct file_operations empty_dir_operations = …;


void make_empty_dir_inode(struct inode *inode)
{ … }

bool is_empty_dir_inode(struct inode *inode)
{ … }

#if IS_ENABLED(CONFIG_UNICODE)
/**
 * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
 * @dentry:	dentry whose name we are checking against
 * @len:	len of name of dentry
 * @str:	str pointer to name of dentry
 * @name:	Name to compare against
 *
 * Return: 0 if names match, 1 if mismatch, or -ERRNO
 */
static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
				const char *str, const struct qstr *name)
{ … }

/**
 * generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
 * @dentry:	dentry of the parent directory
 * @str:	qstr of name whose hash we should fill in
 *
 * Return: 0 if hash was successful or unchanged, and -EINVAL on error
 */
static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
{ … }

static const struct dentry_operations generic_ci_dentry_ops = …;

/**
 * generic_ci_match() - Match a name (case-insensitively) with a dirent.
 * This is a filesystem helper for comparison with directory entries.
 * generic_ci_d_compare should be used in VFS' ->d_compare instead.
 *
 * @parent: Inode of the parent of the dirent under comparison
 * @name: name under lookup.
 * @folded_name: Optional pre-folded name under lookup
 * @de_name: Dirent name.
 * @de_name_len: dirent name length.
 *
 * Test whether a case-insensitive directory entry matches the filename
 * being searched.  If @folded_name is provided, it is used instead of
 * recalculating the casefold of @name.
 *
 * Return: > 0 if the directory entry matches, 0 if it doesn't match, or
 * < 0 on error.
 */
int generic_ci_match(const struct inode *parent,
		     const struct qstr *name,
		     const struct qstr *folded_name,
		     const u8 *de_name, u32 de_name_len)
{ … }
EXPORT_SYMBOL(…);
#endif

#ifdef CONFIG_FS_ENCRYPTION
static const struct dentry_operations generic_encrypted_dentry_ops = …;
#endif

/**
 * generic_set_sb_d_ops - helper for choosing the set of
 * filesystem-wide dentry operations for the enabled features
 * @sb: superblock to be configured
 *
 * Filesystems supporting casefolding and/or fscrypt can call this
 * helper at mount-time to configure sb->s_d_op to best set of dentry
 * operations required for the enabled features. The helper must be
 * called after these have been configured, but before the root dentry
 * is created.
 */
void generic_set_sb_d_ops(struct super_block *sb)
{ … }
EXPORT_SYMBOL(…);

/**
 * inode_maybe_inc_iversion - increments i_version
 * @inode: inode with the i_version that should be updated
 * @force: increment the counter even if it's not necessary?
 *
 * Every time the inode is modified, the i_version field must be seen to have
 * changed by any observer.
 *
 * If "force" is set or the QUERIED flag is set, then ensure that we increment
 * the value, and clear the queried flag.
 *
 * In the common case where neither is set, then we can return "false" without
 * updating i_version.
 *
 * If this function returns false, and no other metadata has changed, then we
 * can avoid logging the metadata.
 */
bool inode_maybe_inc_iversion(struct inode *inode, bool force)
{ … }
EXPORT_SYMBOL(…);

/**
 * inode_query_iversion - read i_version for later use
 * @inode: inode from which i_version should be read
 *
 * Read the inode i_version counter. This should be used by callers that wish
 * to store the returned i_version for later comparison. This will guarantee
 * that a later query of the i_version will result in a different value if
 * anything has changed.
 *
 * In this implementation, we fetch the current value, set the QUERIED flag and
 * then try to swap it into place with a cmpxchg, if it wasn't already set. If
 * that fails, we try again with the newly fetched value from the cmpxchg.
 */
u64 inode_query_iversion(struct inode *inode)
{ … }
EXPORT_SYMBOL(…);

ssize_t direct_write_fallback(struct kiocb *iocb, struct iov_iter *iter,
		ssize_t direct_written, ssize_t buffered_written)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * simple_inode_init_ts - initialize the timestamps for a new inode
 * @inode: inode to be initialized
 *
 * When a new inode is created, most filesystems set the timestamps to the
 * current time. Add a helper to do this.
 */
struct timespec64 simple_inode_init_ts(struct inode *inode)
{ … }
EXPORT_SYMBOL(…);

static inline struct dentry *get_stashed_dentry(struct dentry *stashed)
{ … }

static struct dentry *prepare_anon_dentry(struct dentry **stashed,
					  struct super_block *sb,
					  void *data)
{ … }

static struct dentry *stash_dentry(struct dentry **stashed,
				   struct dentry *dentry)
{ … }

/**
 * path_from_stashed - create path from stashed or new dentry
 * @stashed:    where to retrieve or stash dentry
 * @mnt:        mnt of the filesystems to use
 * @data:       data to store in inode->i_private
 * @path:       path to create
 *
 * The function tries to retrieve a stashed dentry from @stashed. If the dentry
 * is still valid then it will be reused. If the dentry isn't able the function
 * will allocate a new dentry and inode. It will then check again whether it
 * can reuse an existing dentry in case one has been added in the meantime or
 * update @stashed with the newly added dentry.
 *
 * Special-purpose helper for nsfs and pidfs.
 *
 * Return: On success zero and on failure a negative error is returned.
 */
int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, void *data,
		      struct path *path)
{ … }

void stashed_dentry_prune(struct dentry *dentry)
{ … }