VFS_BUSY(9) OpenBSD Kernel Manual VFS_BUSY(9)NAME
vfs_busy, vfs_isbusy, vfs_unbusy - VFS locking API
SYNOPSIS
#include <sys/mount.h>
int
vfs_busy(struct mount *mp, int flags);
int
vfs_isbusy(struct mount *mp);
void
vfs_unbusy(struct mount *mp);
DESCRIPTION
The vfs_busy API is used to lock mount points to ensure consistent
access. A read lock can be shared between multiple processes, while a
write lock is exclusive. Normally a write lock is only acquired when
unmounting.
The vfs_busy() function locks the mount point pointed to by mp, where
flags describes the type of lock to acquire and whether or not to wait
for a conflicting lock to be released. The following flags are
available:
VB_READ Acquire a read lock.
VB_WRITE Acquire a write lock.
VB_NOWAIT Return immediately; do not wait for the conflicting
lock to be released.
VB_WAIT Wait for the conflicting lock to be released.
If a conflicting lock was encountered, vfs_busy() returns an error.
The vfs_isbusy() function checks whether the given mount point is locked.
vfs_unbusy() unlocks the given mount point.
The vfs_busy API is implemented in the file sys/kern/vfs_subr.c.
SEE ALSOrwlock(9), vfs(9)OpenBSD 4.9 May 31, 2007 OpenBSD 4.9
