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.

1 files changed, 6 insertions, 10 deletions

diff --git a/sys/kern/vfs_cluster.c b/sys/kern/vfs_cluster.c
index c9c09cb..b685740 100644
--- a/sys/kern/vfs_cluster.c
+++ b/sys/kern/vfs_cluster.c
@@ -320,6 +320,8 @@ cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
 	daddr_t bn;
 	int i, inc, j;
 
+	GIANT_REQUIRED;
+
 	KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
 	    ("cluster_rbuild: size %ld != filesize %ld\n",
 	    size, vp->v_mount->mnt_stat.f_iosize));
@@ -433,7 +435,6 @@ cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
 		BUF_KERNPROC(tbp);
 		TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
 			tbp, b_cluster.cluster_entry);
-		mtx_lock(&vm_mtx);
 		for (j = 0; j < tbp->b_npages; j += 1) {
 			vm_page_t m;
 			m = tbp->b_pages[j];
@@ -447,12 +448,10 @@ cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
 			if ((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL)
 				tbp->b_pages[j] = bogus_page;
 		}
-		mtx_unlock(&vm_mtx);
 		bp->b_bcount += tbp->b_bcount;
 		bp->b_bufsize += tbp->b_bufsize;
 	}
 
-	mtx_lock(&vm_mtx);
 	for(j=0;j<bp->b_npages;j++) {
 		if ((bp->b_pages[j]->valid & VM_PAGE_BITS_ALL) ==
 			VM_PAGE_BITS_ALL)
@@ -465,7 +464,6 @@ cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
 
 	pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 		(vm_page_t *)bp->b_pages, bp->b_npages);
-	mtx_unlock(&vm_mtx);
 	return (bp);
 }
 
@@ -482,15 +480,15 @@ cluster_callback(bp)
 	struct buf *nbp, *tbp;
 	int error = 0;
 
+	GIANT_REQUIRED;
+
 	/*
 	 * Must propogate errors to all the components.
 	 */
 	if (bp->b_ioflags & BIO_ERROR)
 		error = bp->b_error;
 
-	mtx_lock(&vm_mtx);
 	pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages);
-	mtx_unlock(&vm_mtx);
 	/*
 	 * Move memory from the large cluster buffer into the component
 	 * buffers and mark IO as done on these.
@@ -724,6 +722,8 @@ cluster_wbuild(vp, size, start_lbn, len)
 	int totalwritten = 0;
 	int dbsize = btodb(size);
 
+	GIANT_REQUIRED;
+
 	while (len > 0) {
 		s = splbio();
 		/*
@@ -866,7 +866,6 @@ cluster_wbuild(vp, size, start_lbn, len)
 					}
 				}
 					
-				mtx_lock(&vm_mtx);
 				for (j = 0; j < tbp->b_npages; j += 1) {
 					m = tbp->b_pages[j];
 					vm_page_io_start(m);
@@ -877,7 +876,6 @@ cluster_wbuild(vp, size, start_lbn, len)
 						bp->b_npages++;
 					}
 				}
-				mtx_unlock(&vm_mtx);
 			}
 			bp->b_bcount += size;
 			bp->b_bufsize += size;
@@ -896,10 +894,8 @@ cluster_wbuild(vp, size, start_lbn, len)
 				tbp, b_cluster.cluster_entry);
 		}
 	finishcluster:
-		mtx_lock(&vm_mtx);
 		pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 			(vm_page_t *) bp->b_pages, bp->b_npages);
-		mtx_unlock(&vm_mtx);
 		if (bp->b_bufsize > bp->b_kvasize)
 			panic(
 			    "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",