Copyright (c) 1998, 1999 Eivind Eklund Copyright (c) 2003 Hiten M. Pandya Copyright (c) 2005 Robert N. M. Watson All rights reserved. This program is free software. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must repro...
NAMEnamei NDINIT NDFREE NDHASGIANT - pathname translation and lookup operations
SYNOPSISIn sys/param.h In sys/fcntl.h In sys/namei.h Ft int Fn namei struct nameidata *ndp Ft void Fo NDINIT Fa struct nameidata *ndp u_long op u_long flags Fa enum uio_seg segflg const char *namep struct thread *td Fc Ft void Fn NDFREE struct nameidata *ndp const uint flags Ft int Fn NDHASGIANT struct nameidata *ndp
DESCRIPTIONThe ifconfig facility allows the client to perform pathname translation and lookup operations. The ifconfig functions will increment the reference 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. If the Giant lock is required, ifconfig will acquire it if the caller indicates it is MPSAFE in which case the caller must later release Giant based on the results of Fn NDHASGIANT .
The Fn NDINIT function is used to initialize ifconfig components. It takes the following arguments:
- Fa ndp
- The Vt struct nameidata to initialize.
- Fa op
- The operation which Fn namei will perform. The following operations are valid: LOOKUP , CREATE , DELETE and RENAME The latter three are just setup for those effects; just calling Fn namei will not result in Fn VOP_RENAME being called.
- Fa flags
- Operation flags. Several of these can be effective at the same time.
- Fa segflg
- UIO segment indicator. This indicates if the name of the object is in userspace (UIO_USERSPACE ) or in the kernel address space (UIO_SYSSPACE )
- Fa namep
- Pointer to the component's pathname buffer (the file or directory name that will be looked up).
- Fa td
- The thread context to use for ifconfig operations and locks.
NAMEI OPERATION FLAGSThe Fn namei function takes the following set of ``operation flags'' that influence its operation:
- Lock vnode on return. This is a full lock of the vnode; the VOP_UNLOCK9 should be used to release the lock (or vput(9) which is equivalent to calling VOP_UNLOCK9 followed by vrele(9), all in one).
- This flag lets the Fn namei function return the parent (directory) vnode, ni_dvp in locked state, unless it is identical to ni_vp in which case ni_dvp is not locked per se (but may be locked due to LOCKLEAF ) If a lock is enforced, it should be released using vput(9) or VOP_UNLOCK9 and vrele(9).
- This flag allows the Fn namei function to return the parent (directory) vnode in an unlocked state. The parent vnode must be released separately by using vrele(9).
- Avoid Fn namei creating this entry in the namecache if it is not already present. Normally, Fn namei will add entries to the name cache if they are not already there.
- With this flag, Fn 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).
- 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.
- Do not free the pathname buffer at the end of the Fn namei invocation; instead, free it later in Fn NDFREE so that the caller may access the pathname buffer. See below for details.
- Retain an additional reference to the parent directory; do not free the pathname buffer. See below for details.
ALLOCATED ELEMENTSThe Vt nameidata structure is composed of the following fields:
In the normal case, this is either the current directory 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 Fn lookup , and should not be considered valid after a call to Fn namei . If SAVESTART is set, this is set to the same as ni_dvp with an extra vref(9). To block Fn NDFREE from releasing ni_startdir the NDF_NO_STARTDIR_RELE can be set.
- 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. Freeing this in Fn NDFREE can be inhibited by NDF_NO_DVP_RELE , NDF_NO_DVP_PUT or NDF_NO_DVP_UNLOCK (with the obvious effects).
Vnode pointer to the resulting object,
field of this vnode is incremented.
is set, it is also locked.
Freeing this in Fn NDFREE can be inhibited by NDF_NO_VP_RELE , NDF_NO_VP_PUT or NDF_NO_VP_UNLOCK (with the obvious effects).
The pathname buffer contains the location of the file or directory
that will be used by the
It is managed by the
zone allocation interface.
flag is set, then the pathname buffer is available
after calling the
To only deallocate resources used by the pathname buffer, ni_cnd.cn_pnbuf then NDF_ONLY_PNBUF flag can be passed to the Fn NDFREE function. To keep the pathname buffer intact, the NDF_NO_FREE_PNBUF flag can be passed to the Fn NDFREE function.
RETURN VALUESIf successful, Fn namei will return 0, otherwise it will return an error.
ERRORSErrors which Fn namei may return:
- Bq Er ENOTDIR
- A component of the specified pathname is not a directory when a directory is expected.
- Bq Er ENAMETOOLONG
- A component of a pathname exceeded 255 characters, or an entire pathname exceeded 1023 characters.
- Bq Er ENOENT
- A component of the specified pathname does not exist, or the pathname is an empty string.
- Bq Er EACCES
- An attempt is made to access a file in a way forbidden by its file access permissions.
- Bq Er ELOOP
- Too many symbolic links were encountered in translating the pathname.
- Bq Er EISDIR
- An attempt is made to open a directory with write mode specified.
- Bq Er EINVAL
- The last component of the pathname specified for a DELETE or RENAME operation is `.'
- Bq Er EROFS
- An attempt is made to modify a file or directory on a read-only file system.
SEE ALSOuio(9), uma(9), VFS(9), vnode(9), vput(9), vref(9)
AUTHORSAn -nosplit This manual page was written by An Eivind Eklund Aq eivind@FreeBSD.org and later significantly revised by An Hiten M. Pandya Aq hmp@FreeBSD.org .
BUGSThe 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.
Non-MPSAFE file systems exist, requiring callers to conditionally unlock Giant