MFC r269457:

Remove Giant acquisition from the mount and unmount pathes.

1 files changed, 61 insertions, 32 deletions

diff --git a/sys/kern/vfs_init.c b/sys/kern/vfs_init.c
index eab48fb..dd21743 100644
--- a/sys/kern/vfs_init.c
+++ b/sys/kern/vfs_init.c
@@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/linker.h>
 #include <sys/mount.h>
 #include <sys/proc.h>
+#include <sys/sx.h>
 #include <sys/syscallsubr.h>
 #include <sys/sysctl.h>
 #include <sys/vnode.h>
@@ -64,6 +65,8 @@ int maxvfsconf = VFS_GENERIC + 1;
  * New entries are added/deleted by vfs_register()/vfs_unregister()
  */
 struct vfsconfhead vfsconf = TAILQ_HEAD_INITIALIZER(vfsconf);
+struct sx vfsconf_sx;
+SX_SYSINIT(vfsconf, &vfsconf_sx, "vfsconf");
 
 /*
  * Loader.conf variable vfs.typenumhash enables setting vfc_typenum using a hash
@@ -105,20 +108,33 @@ struct vattr va_null;
  * Routines having to do with the management of the vnode table.
  */
 
-struct vfsconf *
-vfs_byname(const char *name)
+static struct vfsconf *
+vfs_byname_locked(const char *name)
 {
 	struct vfsconf *vfsp;
 
+	sx_assert(&vfsconf_sx, SA_LOCKED);
 	if (!strcmp(name, "ffs"))
 		name = "ufs";
-	TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
+	TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
 		if (!strcmp(name, vfsp->vfc_name))
 			return (vfsp);
+	}
 	return (NULL);
 }
 
 struct vfsconf *
+vfs_byname(const char *name)
+{
+	struct vfsconf *vfsp;
+
+	vfsconf_slock();
+	vfsp = vfs_byname_locked(name);
+	vfsconf_sunlock();
+	return (vfsp);
+}
+
+struct vfsconf *
 vfs_byname_kld(const char *fstype, struct thread *td, int *error)
 {
 	struct vfsconf *vfsp;
@@ -169,8 +185,11 @@ vfs_register(struct vfsconf *vfc)
 		    vfc->vfc_name, vfc->vfc_version);
 		return (EINVAL);
 	}
-	if (vfs_byname(vfc->vfc_name) != NULL)
+	vfsconf_lock();
+	if (vfs_byname_locked(vfc->vfc_name) != NULL) {
+		vfsconf_unlock();
 		return (EEXIST);
+	}
 
 	if (vfs_typenumhash != 0) {
 		/*
@@ -203,26 +222,6 @@ vfs_register(struct vfsconf *vfc)
 	TAILQ_INSERT_TAIL(&vfsconf, vfc, vfc_list);
 
 	/*
-	 * If this filesystem has a sysctl node under vfs
-	 * (i.e. vfs.xxfs), then change the oid number of that node to 
-	 * match the filesystem's type number.  This allows user code
-	 * which uses the type number to read sysctl variables defined
-	 * by the filesystem to continue working. Since the oids are
-	 * in a sorted list, we need to make sure the order is
-	 * preserved by re-registering the oid after modifying its
-	 * number.
-	 */
-	sysctl_lock();
-	SLIST_FOREACH(oidp, &sysctl__vfs_children, oid_link)
-		if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
-			sysctl_unregister_oid(oidp);
-			oidp->oid_number = vfc->vfc_typenum;
-			sysctl_register_oid(oidp);
-			break;
-		}
-	sysctl_unlock();
-
-	/*
 	 * Initialise unused ``struct vfsops'' fields, to use
 	 * the vfs_std*() functions.  Note, we need the mount
 	 * and unmount operations, at the least.  The check
@@ -281,8 +280,30 @@ vfs_register(struct vfsconf *vfc)
 	 * Call init function for this VFS...
 	 */
 	(*(vfc->vfc_vfsops->vfs_init))(vfc);
+	vfsconf_unlock();
 
-	return 0;
+	/*
+	 * If this filesystem has a sysctl node under vfs
+	 * (i.e. vfs.xxfs), then change the oid number of that node to
+	 * match the filesystem's type number.  This allows user code
+	 * which uses the type number to read sysctl variables defined
+	 * by the filesystem to continue working. Since the oids are
+	 * in a sorted list, we need to make sure the order is
+	 * preserved by re-registering the oid after modifying its
+	 * number.
+	 */
+	sysctl_lock();
+	SLIST_FOREACH(oidp, &sysctl__vfs_children, oid_link) {
+		if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
+			sysctl_unregister_oid(oidp);
+			oidp->oid_number = vfc->vfc_typenum;
+			sysctl_register_oid(oidp);
+			break;
+		}
+	}
+	sysctl_unlock();
+
+	return (0);
 }
 
 
@@ -295,15 +316,22 @@ vfs_unregister(struct vfsconf *vfc)
 
 	i = vfc->vfc_typenum;
 
-	vfsp = vfs_byname(vfc->vfc_name);
-	if (vfsp == NULL)
-		return EINVAL;
-	if (vfsp->vfc_refcount)
-		return EBUSY;
+	vfsconf_lock();
+	vfsp = vfs_byname_locked(vfc->vfc_name);
+	if (vfsp == NULL) {
+		vfsconf_unlock();
+		return (EINVAL);
+	}
+	if (vfsp->vfc_refcount != 0) {
+		vfsconf_unlock();
+		return (EBUSY);
+	}
 	if (vfc->vfc_vfsops->vfs_uninit != NULL) {
 		error = (*vfc->vfc_vfsops->vfs_uninit)(vfsp);
-		if (error)
+		if (error != 0) {
+			vfsconf_unlock();
 			return (error);
+		}
 	}
 	TAILQ_REMOVE(&vfsconf, vfsp, vfc_list);
 	maxtypenum = VFS_GENERIC;
@@ -311,7 +339,8 @@ vfs_unregister(struct vfsconf *vfc)
 		if (maxtypenum < vfsp->vfc_typenum)
 			maxtypenum = vfsp->vfc_typenum;
 	maxvfsconf = maxtypenum + 1;
-	return 0;
+	vfsconf_unlock();
+	return (0);
 }
 
 /*