With Alfred's permission, remove vm_mtx in favor of a fine-grained approach

(this commit is just the first stage).  Also add various GIANT_ macros to
formalize the removal of Giant, making it easy to test in a more piecemeal
fashion. These macros will allow us to test fine-grained locks to a degree
before removing Giant, and also after, and to remove Giant in a piecemeal
fashion via sysctl's on those subsystems which the authors believe can
operate without Giant.

3 files changed, 7 insertions, 17 deletions

diff --git a/sys/fs/procfs/procfs_map.c b/sys/fs/procfs/procfs_map.c
index 047a67f..692594d 100644
--- a/sys/fs/procfs/procfs_map.c
+++ b/sys/fs/procfs/procfs_map.c
@@ -81,14 +81,14 @@ procfs_domap(curp, p, pfs, uio)
 	vm_map_entry_t entry;
 	char mebuffer[MEBUFFERSIZE];
 
+	GIANT_REQUIRED;
+
 	if (uio->uio_rw != UIO_READ)
 		return (EOPNOTSUPP);
 
 	if (uio->uio_offset != 0)
 		return (0);
 	
-	mtx_lock(&vm_mtx);
-
 	error = 0;
 	if (map != &curproc->p_vmspace->vm_map)
 		vm_map_lock_read(map);
@@ -171,17 +171,13 @@ case OBJT_DEVICE:
 			error = EFBIG;
 			break;
 		}
-		mtx_unlock(&vm_mtx);
 		error = uiomove(mebuffer, len, uio);
-		mtx_lock(&vm_mtx);
 		if (error)
 			break;
 	}
 	if (map != &curproc->p_vmspace->vm_map)
 		vm_map_unlock_read(map);
 	
-	mtx_unlock(&vm_mtx);
-
 	return error;
 }
 
diff --git a/sys/fs/procfs/procfs_mem.c b/sys/fs/procfs/procfs_mem.c
index b8c60d6..e109146 100644
--- a/sys/fs/procfs/procfs_mem.c
+++ b/sys/fs/procfs/procfs_mem.c
@@ -83,6 +83,8 @@ procfs_rwmem(curp, p, uio)
 	vm_prot_t reqprot;
 	vm_offset_t kva;
 
+	GIANT_REQUIRED;
+
 	/*
 	 * if the vmspace is in the midst of being deallocated or the
 	 * process is exiting, don't try to grab anything.  The page table
@@ -91,12 +93,8 @@ procfs_rwmem(curp, p, uio)
 	vm = p->p_vmspace;
 	if ((p->p_flag & P_WEXIT))
 		return EFAULT;
-
-	mtx_lock(&vm_mtx);
-	if (vm->vm_refcnt < 1) {
-		mtx_unlock(&vm_mtx);
+	if (vm->vm_refcnt < 1)
 		return EFAULT;
-	}
 	++vm->vm_refcnt;
 	/*
 	 * The map we want...
@@ -214,9 +212,7 @@ procfs_rwmem(curp, p, uio)
 		/*
 		 * Now do the i/o move.
 		 */
-		mtx_unlock(&vm_mtx);
 		error = uiomove((caddr_t)(kva + page_offset), len, uio);
-		mtx_lock(&vm_mtx);
 
 		pmap_kremove(kva);
 
@@ -235,7 +231,6 @@ procfs_rwmem(curp, p, uio)
 
 	kmem_free(kernel_map, kva, PAGE_SIZE);
 	vmspace_free(vm);
-	mtx_unlock(&vm_mtx);
 	return (error);
 }
 
diff --git a/sys/fs/specfs/spec_vnops.c b/sys/fs/specfs/spec_vnops.c
index 5ed07c0..f2b1c34 100644
--- a/sys/fs/specfs/spec_vnops.c
+++ b/sys/fs/specfs/spec_vnops.c
@@ -660,7 +660,8 @@ spec_getpages(ap)
 	int blksiz;
 	int gotreqpage;
 
-	mtx_assert(&Giant, MA_OWNED);
+	GIANT_REQUIRED;
+
 	error = 0;
 	pcount = round_page(ap->a_count) / PAGE_SIZE;
 
@@ -732,7 +733,6 @@ spec_getpages(ap)
 	cnt.v_vnodein++;
 	cnt.v_vnodepgsin += pcount;
 
-	mtx_unlock(&vm_mtx);
 	/* Do the input. */
 	BUF_STRATEGY(bp);
 
@@ -743,7 +743,6 @@ spec_getpages(ap)
 		tsleep(bp, PVM, "spread", 0);
 
 	splx(s);
-	mtx_lock(&vm_mtx);
 
 	if ((bp->b_ioflags & BIO_ERROR) != 0) {
 		if (bp->b_error)