Remove the now invalid (and possibly unused) debug.mpsafevfs

sysctl/tunable.

Reviewed by:	emaste
Sponsored by:	Sandvine Incorporated

UPDATING

@@ -22,6 +22,10 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 8.x IS SLOW:
 	to maximize performance.  (To disable malloc debugging, run
 	ln -s aj /etc/malloc.conf.)
 
+20090530:
+	Remove the tunable/sysctl debug.mpsafevfs as its initial purpose
+	is no more valid.
+
 20090530:
 	Add VOP_ACCESSX(9).  File system modules need to be rebuilt.
 	Bump __FreeBSD_version to 800094.

sys/kern/vfs_subr.c

@@ -114,15 +114,6 @@ static void	vfs_knlunlock(void *arg);
 static int	vfs_knllocked(void *arg);
 static void	destroy_vpollinfo(struct vpollinfo *vi);
 
-/*
- * Enable Giant pushdown based on whether or not the vm is mpsafe in this
- * build.  Without mpsafevm the buffer cache can not run Giant free.
- */
-int mpsafe_vfs = 1;
-TUNABLE_INT("debug.mpsafevfs", &mpsafe_vfs);
-SYSCTL_INT(_debug, OID_AUTO, mpsafevfs, CTLFLAG_RD, &mpsafe_vfs, 0,
-    "MPSAFE VFS");
-
 /*
  * Number of vnodes in existence.  Increased whenever getnewvnode()
  * allocates a new vnode, decreased on vdestroy() called on VI_DOOMed

sys/sys/mount.h

@@ -619,10 +619,8 @@ vfs_statfs_t	__vfs_statfs;
 	({if (*(MP)->mnt_op->vfs_susp_clean != NULL)		\
 	       (*(MP)->mnt_op->vfs_susp_clean)(MP); })
 
-extern int mpsafe_vfs;
-
 #define	VFS_NEEDSGIANT_(MP)						\
-    (!mpsafe_vfs || ((MP) != NULL && ((MP)->mnt_kern_flag & MNTK_MPSAFE) == 0))
+    ((MP) != NULL && ((MP)->mnt_kern_flag & MNTK_MPSAFE) == 0)
 
 #define	VFS_NEEDSGIANT(MP) __extension__				\
 ({									\