NAME

     VFS_LOCK_GIANT, VFS_UNLOCK_GIANT — conditionally lock and unlock Giant around entry into VFS

SYNOPSIS

     #include <sys/param.h>
     #include <sys/mount.h>
     #include <sys/vnode.h>

     int
     VFS_LOCK_GIANT(struct mount *mp);

     void
     VFS_UNLOCK_GIANT(int vfslocked);

DESCRIPTION

     VFS_LOCK_GIANT() will conditionally acquire the Giant lock if the file system referenced by
     mp is marked as MPSAFE or not, returning a flag indicating whether Giant was set, which may
     later be passed to VFS_UNLOCK_GIANT().  The value of mp will typically be derived from the
     mount pointer in a vnode on which a VFS operation will be performed.

     VFS_UNLOCK_GIANT() conditionally releases the Giant lock if the passed vfslocked argument is
     non-zero.  It is expected that the argument will be derived from the return values of
     VFS_LOCK_GIANT() or NDHASGIANT(9).

RETURN VALUES

     VFS_LOCK_GIANT() returns a boolean indicating whether or not Giant was acquired.

SEE ALSO

     mutex(9), NDHASGIANT(9), vnode(9)

AUTHORS

     MPSAFE VFS support for FreeBSD was implemented by Jeff Roberson.

     This manual page was written by Robert Watson.

BUGS

     Non-MPSAFE file systems exist, requiring callers conditional locking and unlocking of Giant.