MFC r269457:

Remove Giant acquisition from the mount and unmount pathes.

3 files changed, 87 insertions, 65 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);
 }
 
 /*
diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index 8b764f7..674e526 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -463,9 +463,9 @@ vfs_mount_alloc(struct vnode *vp, struct vfsconf *vfsp, const char *fspath,
 	mp->mnt_activevnodelistsize = 0;
 	mp->mnt_ref = 0;
 	(void) vfs_busy(mp, MBF_NOWAIT);
+	atomic_add_acq_int(&vfsp->vfc_refcount, 1);
 	mp->mnt_op = vfsp->vfc_vfsops;
 	mp->mnt_vfc = vfsp;
-	vfsp->vfc_refcount++;	/* XXX Unlocked */
 	mp->mnt_stat.f_type = vfsp->vfc_typenum;
 	mp->mnt_gen++;
 	strlcpy(mp->mnt_stat.f_fstypename, vfsp->vfc_name, MFSNAMELEN);
@@ -505,7 +505,7 @@ vfs_mount_destroy(struct mount *mp)
 		panic("vfs_mount_destroy: nonzero writeopcount");
 	if (mp->mnt_secondary_writes != 0)
 		panic("vfs_mount_destroy: nonzero secondary_writes");
-	mp->mnt_vfc->vfc_refcount--;
+	atomic_subtract_rel_int(&mp->mnt_vfc->vfc_refcount, 1);
 	if (!TAILQ_EMPTY(&mp->mnt_nvnodelist)) {
 		struct vnode *vp;
 
@@ -736,17 +736,12 @@ sys_mount(td, uap)
 	}
 
 	AUDIT_ARG_TEXT(fstype);
-	mtx_lock(&Giant);
 	vfsp = vfs_byname_kld(fstype, td, &error);
 	free(fstype, M_TEMP);
-	if (vfsp == NULL) {
-		mtx_unlock(&Giant);
+	if (vfsp == NULL)
 		return (ENOENT);
-	}
-	if (vfsp->vfc_vfsops->vfs_cmount == NULL) {
-		mtx_unlock(&Giant);
+	if (vfsp->vfc_vfsops->vfs_cmount == NULL)
 		return (EOPNOTSUPP);
-	}
 
 	ma = mount_argsu(ma, "fstype", uap->type, MFSNAMELEN);
 	ma = mount_argsu(ma, "fspath", uap->path, MNAMELEN);
@@ -755,7 +750,6 @@ sys_mount(td, uap)
 	ma = mount_argb(ma, !(flags & MNT_NOEXEC), "noexec");
 
 	error = vfsp->vfc_vfsops->vfs_cmount(ma, uap->data, flags);
-	mtx_unlock(&Giant);
 	return (error);
 }
 
@@ -777,7 +771,6 @@ vfs_domount_first(
 	struct vnode *newdp;
 	int error;
 
-	mtx_assert(&Giant, MA_OWNED);
 	ASSERT_VOP_ELOCKED(vp, __func__);
 	KASSERT((fsflags & MNT_UPDATE) == 0, ("MNT_UPDATE shouldn't be here"));
 
@@ -889,7 +882,6 @@ vfs_domount_update(
 	int error, export_error;
 	uint64_t flag;
 
-	mtx_assert(&Giant, MA_OWNED);
 	ASSERT_VOP_ELOCKED(vp, __func__);
 	KASSERT((fsflags & MNT_UPDATE) != 0, ("MNT_UPDATE should be here"));
 
@@ -1091,7 +1083,6 @@ vfs_domount(
 	error = namei(&nd);
 	if (error != 0)
 		return (error);
-	mtx_lock(&Giant);
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	vp = nd.ni_vp;
 	if ((fsflags & MNT_UPDATE) == 0) {
@@ -1106,7 +1097,6 @@ vfs_domount(
 		free(pathbuf, M_TEMP);
 	} else
 		error = vfs_domount_update(td, vp, fsflags, optlist);
-	mtx_unlock(&Giant);
 
 	ASSERT_VI_UNLOCKED(vp, __func__);
 	ASSERT_VOP_UNLOCKED(vp, __func__);
@@ -1153,12 +1143,10 @@ sys_unmount(td, uap)
 		free(pathbuf, M_TEMP);
 		return (error);
 	}
-	mtx_lock(&Giant);
 	if (uap->flags & MNT_BYFSID) {
 		AUDIT_ARG_TEXT(pathbuf);
 		/* Decode the filesystem ID. */
 		if (sscanf(pathbuf, "FSID:%d:%d", &id0, &id1) != 2) {
-			mtx_unlock(&Giant);
 			free(pathbuf, M_TEMP);
 			return (EINVAL);
 		}
@@ -1198,19 +1186,15 @@ sys_unmount(td, uap)
 		 * now, so in the !MNT_BYFSID case return the more likely
 		 * EINVAL for compatibility.
 		 */
-		mtx_unlock(&Giant);
 		return ((uap->flags & MNT_BYFSID) ? ENOENT : EINVAL);
 	}
 
 	/*
 	 * Don't allow unmounting the root filesystem.
 	 */
-	if (mp->mnt_flag & MNT_ROOTFS) {
-		mtx_unlock(&Giant);
+	if (mp->mnt_flag & MNT_ROOTFS)
 		return (EINVAL);
-	}
 	error = dounmount(mp, uap->flags, td);
-	mtx_unlock(&Giant);
 	return (error);
 }
 
@@ -1228,8 +1212,6 @@ dounmount(mp, flags, td)
 	uint64_t async_flag;
 	int mnt_gen_r;
 
-	mtx_assert(&Giant, MA_OWNED);
-
 	if ((coveredvp = mp->mnt_vnodecovered) != NULL) {
 		mnt_gen_r = mp->mnt_gen;
 		VI_LOCK(coveredvp);
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 9f34eda..9c90fe5 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -3231,6 +3231,7 @@ sysctl_vfs_conflist(SYSCTL_HANDLER_ARGS)
 	int error;
 
 	error = 0;
+	vfsconf_slock();
 	TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
 #ifdef COMPAT_FREEBSD32
 		if (req->flags & SCTL_MASK32)
@@ -3241,11 +3242,12 @@ sysctl_vfs_conflist(SYSCTL_HANDLER_ARGS)
 		if (error)
 			break;
 	}
+	vfsconf_sunlock();
 	return (error);
 }
 
-SYSCTL_PROC(_vfs, OID_AUTO, conflist, CTLTYPE_OPAQUE | CTLFLAG_RD,
-    NULL, 0, sysctl_vfs_conflist,
+SYSCTL_PROC(_vfs, OID_AUTO, conflist, CTLTYPE_OPAQUE | CTLFLAG_RD |
+    CTLFLAG_MPSAFE, NULL, 0, sysctl_vfs_conflist,
     "S,xvfsconf", "List of all configured filesystems");
 
 #ifndef BURN_BRIDGES
@@ -3275,9 +3277,12 @@ vfs_sysctl(SYSCTL_HANDLER_ARGS)
 	case VFS_CONF:
 		if (namelen != 3)
 			return (ENOTDIR);	/* overloaded */
-		TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
+		vfsconf_slock();
+		TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
 			if (vfsp->vfc_typenum == name[2])
 				break;
+		}
+		vfsconf_sunlock();
 		if (vfsp == NULL)
 			return (EOPNOTSUPP);
 #ifdef COMPAT_FREEBSD32
@@ -3290,8 +3295,9 @@ vfs_sysctl(SYSCTL_HANDLER_ARGS)
 	return (EOPNOTSUPP);
 }
 
-static SYSCTL_NODE(_vfs, VFS_GENERIC, generic, CTLFLAG_RD | CTLFLAG_SKIP,
-    vfs_sysctl, "Generic filesystem");
+static SYSCTL_NODE(_vfs, VFS_GENERIC, generic, CTLFLAG_RD | CTLFLAG_SKIP |
+    CTLFLAG_MPSAFE, vfs_sysctl,
+    "Generic filesystem");
 
 #if 1 || defined(COMPAT_PRELITE2)
 
@@ -3302,6 +3308,7 @@ sysctl_ovfs_conf(SYSCTL_HANDLER_ARGS)
 	struct vfsconf *vfsp;
 	struct ovfsconf ovfs;
 
+	vfsconf_slock();
 	TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
 		bzero(&ovfs, sizeof(ovfs));
 		ovfs.vfc_vfsops = vfsp->vfc_vfsops;	/* XXX used as flag */
@@ -3310,10 +3317,13 @@ sysctl_ovfs_conf(SYSCTL_HANDLER_ARGS)
 		ovfs.vfc_refcount = vfsp->vfc_refcount;
 		ovfs.vfc_flags = vfsp->vfc_flags;
 		error = SYSCTL_OUT(req, &ovfs, sizeof ovfs);
-		if (error)
-			return error;
+		if (error != 0) {
+			vfsconf_sunlock();
+			return (error);
+		}
 	}
-	return 0;
+	vfsconf_sunlock();
+	return (0);
 }
 
 #endif /* 1 || COMPAT_PRELITE2 */
@@ -3411,8 +3421,9 @@ sysctl_vnode(SYSCTL_HANDLER_ARGS)
 	return (error);
 }
 
-SYSCTL_PROC(_kern, KERN_VNODE, vnode, CTLTYPE_OPAQUE|CTLFLAG_RD,
-    0, 0, sysctl_vnode, "S,xvnode", "");
+SYSCTL_PROC(_kern, KERN_VNODE, vnode, CTLTYPE_OPAQUE | CTLFLAG_RD |
+    CTLFLAG_MPSAFE, 0, 0, sysctl_vnode, "S,xvnode",
+    "");
 #endif
 
 /*