linux-stable-mirror/include/linux/namei.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_NAMEI_H
#define _LINUX_NAMEI_H

#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/path.h>
#include <linux/fcntl.h>
#include <linux/errno.h>
#include <linux/fs_struct.h>

enum { MAX_NESTED_LINKS = 8 };

#define MAXSYMLINKS 40

/* pathwalk mode */
#define LOOKUP_FOLLOW		BIT(0)	/* follow links at the end */
#define LOOKUP_DIRECTORY	BIT(1)	/* require a directory */
#define LOOKUP_AUTOMOUNT	BIT(2)  /* force terminal automount */
#define LOOKUP_EMPTY		BIT(3)	/* accept empty path [user_... only] */
#define LOOKUP_LINKAT_EMPTY	BIT(4) /* Linkat request with empty path. */
#define LOOKUP_DOWN		BIT(5)	/* follow mounts in the starting point */
#define LOOKUP_MOUNTPOINT	BIT(6)	/* follow mounts in the end */
#define LOOKUP_REVAL		BIT(7)	/* tell ->d_revalidate() to trust no cache */
#define LOOKUP_RCU		BIT(8)	/* RCU pathwalk mode; semi-internal */
#define LOOKUP_CACHED		BIT(9) /* Only do cached lookup */
#define LOOKUP_PARENT		BIT(10)	/* Looking up final parent in path */
/* 5 spare bits for pathwalk */

/* These tell filesystem methods that we are dealing with the final component... */
#define LOOKUP_OPEN		BIT(16)	/* ... in open */
#define LOOKUP_CREATE		BIT(17)	/* ... in object creation */
#define LOOKUP_EXCL		BIT(18)	/* ... in target must not exist */
#define LOOKUP_RENAME_TARGET	BIT(19)	/* ... in destination of rename() */

/* 4 spare bits for intent */

/* Scoping flags for lookup. */
#define LOOKUP_NO_SYMLINKS	BIT(24) /* No symlink crossing. */
#define LOOKUP_NO_MAGICLINKS	BIT(25) /* No nd_jump_link() crossing. */
#define LOOKUP_NO_XDEV		BIT(26) /* No mountpoint crossing. */
#define LOOKUP_BENEATH		BIT(27) /* No escaping from starting point. */
#define LOOKUP_IN_ROOT		BIT(28) /* Treat dirfd as fs root. */
/* LOOKUP_* flags which do scope-related checks based on the dirfd. */
#define LOOKUP_IS_SCOPED (LOOKUP_BENEATH | LOOKUP_IN_ROOT)
/* 3 spare bits for scoping */

extern int path_pts(struct path *path);

extern int user_path_at(int, const char __user *, unsigned, struct path *);

extern int kern_path(const char *, unsigned, struct path *);
struct dentry *kern_path_parent(const char *name, struct path *parent);

extern struct dentry *start_creating_path(int, const char *, struct path *, unsigned int);
extern struct dentry *start_creating_user_path(int, const char __user *, struct path *, unsigned int);
extern void end_creating_path(const struct path *, struct dentry *);
extern struct dentry *start_removing_path(const char *, struct path *);
static inline void end_removing_path(const struct path *path , struct dentry *dentry)
{
	end_creating_path(path, dentry);
}
int vfs_path_parent_lookup(struct filename *filename, unsigned int flags,
			   struct path *parent, struct qstr *last,
			   const struct path *root);
int vfs_path_lookup(struct dentry *, struct vfsmount *, const char *,
		    unsigned int, struct path *);

extern struct dentry *try_lookup_noperm(struct qstr *, struct dentry *);
extern struct dentry *lookup_noperm(struct qstr *, struct dentry *);
extern struct dentry *lookup_noperm_unlocked(struct qstr *, struct dentry *);
extern struct dentry *lookup_noperm_positive_unlocked(struct qstr *, struct dentry *);
struct dentry *lookup_one(struct mnt_idmap *, struct qstr *, struct dentry *);
struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
				   struct qstr *name, struct dentry *base);
struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
					    struct qstr *name,
					    struct dentry *base);
struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap,
					    struct qstr *name,
					    struct dentry *base);

struct dentry *start_creating(struct mnt_idmap *idmap, struct dentry *parent,
			      struct qstr *name);
struct dentry *start_removing(struct mnt_idmap *idmap, struct dentry *parent,
			      struct qstr *name);
struct dentry *start_creating_killable(struct mnt_idmap *idmap,
				       struct dentry *parent,
				       struct qstr *name);
struct dentry *start_removing_killable(struct mnt_idmap *idmap,
				       struct dentry *parent,
				       struct qstr *name);
struct dentry *start_creating_noperm(struct dentry *parent, struct qstr *name);
struct dentry *start_removing_noperm(struct dentry *parent, struct qstr *name);
struct dentry *start_creating_dentry(struct dentry *parent,
				     struct dentry *child);
struct dentry *start_removing_dentry(struct dentry *parent,
				     struct dentry *child);

/* end_creating - finish action started with start_creating
 * @child: dentry returned by start_creating() or vfs_mkdir()
 *
 * Unlock and release the child. This can be called after
 * start_creating() whether that function succeeded or not,
 * but it is not needed on failure.
 *
 * If vfs_mkdir() was called then the value returned from that function
 * should be given for @child rather than the original dentry, as vfs_mkdir()
 * may have provided a new dentry.
 *
 *
 * If vfs_mkdir() was not called, then @child will be a valid dentry and
 * @parent will be ignored.
 */
static inline void end_creating(struct dentry *child)
{
	end_dirop(child);
}

/* end_creating_keep - finish action started with start_creating() and return result
 * @child: dentry returned by start_creating() or vfs_mkdir()
 *
 * Unlock and return the child. This can be called after
 * start_creating() whether that function succeeded or not,
 * but it is not needed on failure.
 *
 * If vfs_mkdir() was called then the value returned from that function
 * should be given for @child rather than the original dentry, as vfs_mkdir()
 * may have provided a new dentry.
 *
 * Returns: @child, which may be a dentry or an error.
 *
 */
static inline struct dentry *end_creating_keep(struct dentry *child)
{
	if (!IS_ERR(child))
		dget(child);
	end_dirop(child);
	return child;
}

/**
 * end_removing - finish action started with start_removing
 * @child:  dentry returned by start_removing()
 * @parent: dentry given to start_removing()
 *
 * Unlock and release the child.
 *
 * This is identical to end_dirop().  It can be passed the result of
 * start_removing() whether that was successful or not, but it not needed
 * if start_removing() failed.
 */
static inline void end_removing(struct dentry *child)
{
	end_dirop(child);
}

extern int follow_down_one(struct path *);
extern int follow_down(struct path *path, unsigned int flags);
extern int follow_up(struct path *);

int start_renaming(struct renamedata *rd, int lookup_flags,
		   struct qstr *old_last, struct qstr *new_last);
int start_renaming_dentry(struct renamedata *rd, int lookup_flags,
			  struct dentry *old_dentry, struct qstr *new_last);
int start_renaming_two_dentries(struct renamedata *rd,
				struct dentry *old_dentry, struct dentry *new_dentry);
void end_renaming(struct renamedata *rd);

/**
 * mode_strip_umask - handle vfs umask stripping
 * @dir:	parent directory of the new inode
 * @mode:	mode of the new inode to be created in @dir
 *
 * In most filesystems, umask stripping depends on whether or not the
 * filesystem supports POSIX ACLs. If the filesystem doesn't support it umask
 * stripping is done directly in here. If the filesystem does support POSIX
 * ACLs umask stripping is deferred until the filesystem calls
 * posix_acl_create().
 *
 * Some filesystems (like NFSv4) also want to avoid umask stripping by the
 * VFS, but don't support POSIX ACLs. Those filesystems can set SB_I_NOUMASK
 * to get this effect without declaring that they support POSIX ACLs.
 *
 * Returns: mode
 */
static inline umode_t __must_check mode_strip_umask(const struct inode *dir, umode_t mode)
{
	if (!IS_POSIXACL(dir) && !(dir->i_sb->s_iflags & SB_I_NOUMASK))
		mode &= ~current_umask();
	return mode;
}

extern int __must_check nd_jump_link(const struct path *path);

static inline void nd_terminate_link(void *name, size_t len, size_t maxlen)
{
	((char *) name)[min(len, maxlen)] = '\0';
}

/**
 * retry_estale - determine whether the caller should retry an operation
 * @error: the error that would currently be returned
 * @flags: flags being used for next lookup attempt
 *
 * Check to see if the error code was -ESTALE, and then determine whether
 * to retry the call based on whether "flags" already has LOOKUP_REVAL set.
 *
 * Returns true if the caller should try the operation again.
 */
static inline bool
retry_estale(const long error, const unsigned int flags)
{
	return unlikely(error == -ESTALE && !(flags & LOOKUP_REVAL));
}

#endif /* _LINUX_NAMEI_H */