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NAMEI(9) Kernel Developer's Manual NAMEI(9) NAME namei, NDINIT, NDINIT_AT, NDFREE_PNBUF -- pathname translation and lookup operations SYNOPSIS #include <sys/param.h> #include <sys/fcntl.h> #include <sys/namei.h> int namei(struct nameidata *ndp); void NDINIT(struct nameidata *ndp, enum nameiop op, u_int64_t flags, enum uio_seg segflg, const char *namep); void NDINIT_AT(struct nameidata *ndp, enum nameiop op, u_int64_t flags, enum uio_seg segflg, const char *namep, int dirfd); void NDFREE_PNBUF(struct nameidata *ndp); DESCRIPTION The namei facility allows the client to perform pathname translation and lookup operations. The namei functions will increment the refer- ence count for the vnode in question. The reference count has to be decremented after use of the vnode, by using either vrele(9) or vput(9), depending on whether the LOCKLEAF flag was specified or not. The NDINIT() macro is used to initialize namei components. It takes the following arguments: ndp A pointer to the struct nameidata to initialize. op The operation which namei() will perform. The following opera- tions are valid: LOOKUP, CREATE, DELETE, and RENAME. The lat- ter three are just setup for those effects; just calling namei() will not result in VOP_RENAME() being called. flags Operation flags, described in the next section. Several of these can be effective at the same time. segflg UIO segment indicator. This indicates if the name of the ob- ject is in userspace (UIO_USERSPACE) or in the kernel address space (UIO_SYSSPACE). namep Pointer to the component's pathname buffer (the file or direc- tory name that will be looked up). The NDINIT_AT() macro is similar to NDINIT(), but takes one extra argu- ment: dirfd File descriptor referencing a directory, or the special value AT_FDCWD meaning the calling thread's current working direc- tory. Lookups will be performed relative to this directory. The NDFREE_PNBUF() macro is used to free the pathname buffer. It must be called exactly once for each successful namei() call. It takes the following argument: ndp A pointer to a struct nameidata that was used in a successful namei() call. NAMEI OPERATION FLAGS The namei() function takes the following set of "operation flags" that influence its operation: LOCKLEAF Lock vnode on return with LK_EXCLUSIVE unless LOCKSHARED is also set. VOP_UNLOCK(9) should be used to release the lock (or vput(9) which is equivalent to calling VOP_UNLOCK(9) followed by vrele(9), all in one). LOCKPARENT This flag lets the namei() function return the parent (di- rectory) vnode, ni_dvp in locked state, unless it is iden- tical to ni_vp, in which case ni_dvp is not locked per se (but may be locked due to LOCKLEAF). If a lock is en- forced, it should be released using vput(9) or VOP_UNLOCK(9) and vrele(9). LOCKSHARED Lock vnode on return with LK_SHARED, if permitted by the file system that owns the vnode. The file system must ex- plicitly permit this by setting MNTK_LOOKUP_SHARED in mp->mnt_kern_flag during mount and by calling VN_LOCK_ASHARE() when allocating the vnode. If LOCKLEAF is specified but shared locking is not permitted, then the vn- ode will be returned with LK_EXCLUSIVE. VOP_UNLOCK(9) should be used to release the lock (or vput(9) which is equivalent to calling VOP_UNLOCK(9) followed by vrele(9), all in one). WANTPARENT This flag allows the namei() function to return the parent (directory) vnode in an unlocked state. The parent vnode must be released separately by using vrele(9). NOCACHE Avoid namei() creating this entry in the namecache if it is not already present. Normally, namei() will add entries to the name cache if they are not already there. FOLLOW With this flag, namei() will follow the symbolic link if the last part of the path supplied is a symbolic link (i.e., it will return a vnode for whatever the link points at, instead for the link itself). NOFOLLOW Do not follow symbolic links (pseudo). This flag is not looked for by the actual code, which looks for FOLLOW. NOFOLLOW is used to indicate to the source code reader that symlinks are intentionally not followed. ALLOCATED ELEMENTS The nameidata structure is composed of the following fields: ni_startdir In the normal case, this is either the current direc- tory or the root. It is the current directory if the name passed in does not start with `/' and we have not gone through any symlinks with an absolute path, and the root otherwise. In this case, it is only used by vfs_lookup(), and should not be considered valid after a call to namei(). ni_dvp Vnode pointer to directory of the object on which lookup is performed. This is available on successful return if LOCKPARENT or WANTPARENT is set. It is locked if LOCKPARENT is set. ni_vp Vnode pointer to the resulting object, NULL otherwise. The v_usecount field of this vnode is incremented. If LOCKLEAF is set, it is also locked. ni_cnd.cn_pnbuf The pathname buffer contains the location of the file or directory that will be used by the namei opera- tions. It is managed by the uma(9) zone allocation interface. RETURN VALUES If successful, namei() will return 0, otherwise it will return an er- ror. FILES src/sys/kern/vfs_lookup.c ERRORS Errors which namei() may return: [ENOTDIR] A component of the specified pathname is not a di- rectory when a directory is expected. [ENAMETOOLONG] A component of a pathname exceeded 255 characters, or an entire pathname exceeded 1023 characters. [ENOENT] A component of the specified pathname does not ex- ist, or the pathname is an empty string. [EACCES] An attempt is made to access a file in a way forbid- den by its file access permissions. [ELOOP] Too many symbolic links were encountered in trans- lating the pathname. [EISDIR] An attempt is made to open a directory with write mode specified. [EINVAL] The last component of the pathname specified for a DELETE or RENAME operation is `.'. [EROFS] An attempt is made to modify a file or directory on a read-only file system. SEE ALSO uio(9), uma(9), VFS(9), vnode(9), vput(9), vref(9), vrele(9) AUTHORS This manual page was written by Eivind Eklund <eivind@FreeBSD.org> and later significantly revised by Hiten M. Pandya <hmp@FreeBSD.org>. BUGS The LOCKPARENT flag does not always result in the parent vnode being locked. This results in complications when the LOCKPARENT is used. In order to solve this for the cases where both LOCKPARENT and LOCKLEAF are used, it is necessary to resort to recursive locking. FreeBSD 14.3 May 16, 2025 NAMEI(9)
NAME | SYNOPSIS | DESCRIPTION | NAMEI OPERATION FLAGS | ALLOCATED ELEMENTS | RETURN VALUES | FILES | ERRORS | SEE ALSO | AUTHORS | BUGS
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