VOP_LOCK, VOP_UNLOCK, VOP_ISLOCKED, vn_lock — serialize access to a vnode

       This manual page was written by Doug Rabson.

Debian                                          February 25, 2008                                    VOP_LOCK(9)

       These  calls  are  used to serialize access to the file system, such as to prevent two writes to the same
       file from happening at the same time.

       The arguments are:

       vp     The vnode being locked or unlocked.

       flags  One of the lock request types:

                    LK_SHARED      Shared lock.
                    LK_EXCLUSIVE   Exclusive lock.
                    LK_UPGRADE     Shared-to-exclusive upgrade.
                    LK_DOWNGRADE   Exclusive-to-shared downgrade.
                    LK_RELEASE     Release any type of lock.
                    LK_DRAIN       Wait for all lock activity to end.

              The lock type may be or'ed with these lock flags:

                    LK_NOWAIT      Do not sleep to wait for lock.
                    LK_SLEEPFAIL   Sleep, then return failure.
                    LK_CANRECURSE  Allow recursive exclusive lock.
                    LK_NOWITNESS   Instruct witness(4) to ignore this instance.

              The lock type may be or'ed with these control flags:

                    LK_INTERLOCK   Specify when the caller already has a simple lock (VOP_LOCK() will unlock the
                                   simple lock after getting the lock).
                    LK_RETRY       Retry until locked.

              Kernel code should use vn_lock()  to  lock  a  vnode  rather  than  calling  VOP_LOCK()  directly.
              vn_lock() also does not want a thread specified as argument but it assumes curthread to be used.

       VOP_LOCK, VOP_UNLOCK, VOP_ISLOCKED, vn_lock — serialize access to a vnode

       Zero is returned on success, otherwise an error is returned.

vnode(9)

#include<sys/param.h>#include<sys/lock.h>#include<sys/vnode.h>intVOP_LOCK(structvnode*vp, intflags);

       intVOP_UNLOCK(structvnode*vp, intflags);

       intVOP_ISLOCKED(structvnode*vp);

       intvn_lock(structvnode*vp, intflags);