NAME
vget —
Acquire a primary reference, lock, and
reactivate a vnode
SYNOPSIS
#include
<sys/param.h>
#include <sys/vnode.h>
int
vget(struct
vnode *vp, int
lockflag);
DESCRIPTION
Acquire a primary reference to vnode and lock it, reactivating the vnode from the cache or free list if necessary. This kernel function must be used if the vnode in hand is not already known to be actively referenced, such as when obtaining the vnode pointer from a namecache or VM object structure.- vp
- The vnode being acquired, typically obtained from some other system structure.
- lockflag
- Must be
LK_SHAREDorLK_EXCLUSIVE. Passing 0 is illegal.LK_NOWAITmay be logically ORd in if you do not wish to block and can handle the additional error codes that might be returned.
When not in use, vnodes are kept on a free list or marked as being cached. The vnodes still reference valid files but may be reused to refer to a new file at any time. Often, references to these vnodes are present in auxiliary structures related to the vnode, such as namecache entries and VM objects.
When acquiring a vnode pointer from these auxiliary structures the
vget function must be used to both reference and, if
necessary, reactivate the vnode. The vnode will also be locked
accordingly.
RETURN VALUES
0 is returned on success, ENOENT is
returned if the vnode becomes unusable while vget is
blocked trying to lock it, and other errors may be returned as well.
ENOENT is not typically considered to be a fatal
error but simply an indication that the caller needs to relookup the vnode
as related structures may be in the midst of being destroyed.
SEE ALSO
vdrop(9), vhold(9), vnode(9), vn_lock(9), vn_unlock(9), vput(9), vref(9), vrele(9)
AUTHORS
This manual page was written by Doug Rabson.