Introduce a new kevent filter. EVFILT_FS that will be used to signal

generic filesystem events to userspace.  Currently only mount and unmount
of filesystems are signalled.  Soon to be added, up/down status of NFS.

Introduce a sysctl node used to route requests to/from filesystems
based on filesystem ids.

Introduce a new vfsop, vfs_sysctl(mp, req) that is used as the callback/
entrypoint by the sysctl code to change individual filesystems.

5 files changed, 131 insertions, 1 deletions

diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
index 0a9aaad..bd0e6d9 100644
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -132,6 +132,7 @@ struct filterops null_filtops =
 	{ 0, filt_nullattach, NULL, NULL };
 
 extern struct filterops sig_filtops;
+extern struct filterops fs_filtops;
 
 /*
  * Table for for all system-defined filters.
@@ -145,6 +146,7 @@ static struct filterops *sysfilt_ops[] = {
 	&sig_filtops,			/* EVFILT_SIGNAL */
 	&timer_filtops,			/* EVFILT_TIMER */
 	&file_filtops,			/* EVFILT_NETDEV */
+	&fs_filtops,			/* EVFILT_FS */
 };
 
 static int
diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index fc39a6b..d759646 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -928,6 +928,7 @@ update:
 		mtx_lock(&mountlist_mtx);
 		TAILQ_INSERT_TAIL(&mountlist, mp, mnt_list);
 		mtx_unlock(&mountlist_mtx);
+		vfs_event_signal(NULL, VQ_MOUNT, NULL);
 		if (VFS_ROOT(mp, &newdp))
 			panic("mount: lost mount");
 		checkdirs(vp, newdp);
@@ -1173,6 +1174,7 @@ dounmount(mp, flags, td)
 	if ((coveredvp = mp->mnt_vnodecovered) != NULL)
 		coveredvp->v_mountedhere = NULL;
 	mtx_unlock(&mountlist_mtx);
+	vfs_event_signal(NULL, VQ_UNMOUNT, NULL);
 	vfs_mount_destroy(mp, td);
 	if (coveredvp != NULL)
 		vrele(coveredvp);
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index af6106a..daef020 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -49,6 +49,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/bio.h>
 #include <sys/buf.h>
 #include <sys/conf.h>
+#include <sys/event.h>
 #include <sys/eventhandler.h>
 #include <sys/extattr.h>
 #include <sys/fcntl.h>
@@ -3906,3 +3907,64 @@ vop_unlock_post(void *ap, int rc)
 		ASSERT_VI_UNLOCKED(a->a_vp, "VOP_UNLOCK");
 }
 #endif /* DEBUG_VFS_LOCKS */
+
+static struct klist fs_klist = SLIST_HEAD_INITIALIZER(&fs_klist);
+
+void
+vfs_event_signal(fsid_t *fsid, u_int32_t event, void *data __unused)
+{
+
+	KNOTE(&fs_klist, event);
+}
+
+static int	filt_fsattach(struct knote *kn);
+static void	filt_fsdetach(struct knote *kn);
+static int	filt_fsevent(struct knote *kn, long hint);
+
+struct filterops fs_filtops =
+	{ 0, filt_fsattach, filt_fsdetach, filt_fsevent };
+
+static int
+filt_fsattach(struct knote *kn)
+{
+
+	kn->kn_flags |= EV_CLEAR;
+	SLIST_INSERT_HEAD(&fs_klist, kn, kn_selnext);
+	return (0);
+}
+
+static void
+filt_fsdetach(struct knote *kn)
+{
+
+	SLIST_REMOVE(&fs_klist, kn, knote, kn_selnext);
+}
+
+static int
+filt_fsevent(struct knote *kn, long hint)
+{
+
+	kn->kn_fflags |= hint;
+	return (kn->kn_fflags != 0);
+}
+
+static int
+sysctl_vfs_ctl(SYSCTL_HANDLER_ARGS)
+{
+	struct vfsidctl vc;
+	int error;
+	struct mount *mp;
+
+	error = SYSCTL_IN(req, &vc, sizeof(vc));
+	if (error)
+		return (error);
+
+	mp = vfs_getvfs(&vc.vc_fsid);
+	if (mp == NULL)
+		return (ENOENT);
+	VCTLTOREQ(&vc, req);
+	return (VFS_SYSCTL(mp, req));
+}
+
+SYSCTL_PROC(_vfs, OID_AUTO, ctl, CTLFLAG_RD,
+        NULL, 0, sysctl_vfs_ctl, "", "Message queue IDs");
diff --git a/sys/sys/event.h b/sys/sys/event.h
index 900089c..b735dd5 100644
--- a/sys/sys/event.h
+++ b/sys/sys/event.h
@@ -37,8 +37,9 @@
 #define EVFILT_SIGNAL		(-6)	/* attached to struct proc */
 #define EVFILT_TIMER		(-7)	/* timers */
 #define EVFILT_NETDEV		(-8)	/* network devices */
+#define EVFILT_FS		(-9)	/* filesystem events */
 
-#define EVFILT_SYSCOUNT		8
+#define EVFILT_SYSCOUNT		9
 
 #define EV_SET(kevp_, a, b, c, d, e, f) do {	\
 	struct kevent *kevp = (kevp_);		\
diff --git a/sys/sys/mount.h b/sys/sys/mount.h
index 735216a..251605a 100644
--- a/sys/sys/mount.h
+++ b/sys/sys/mount.h
@@ -380,6 +380,62 @@ struct ovfsconf {
 #define	VFCF_LOOPBACK	0x00100000	/* aliases some other mounted FS */
 #define	VFCF_UNICODE	0x00200000	/* stores file names as Unicode*/
 
+struct vfsidctl {
+	int		vc_vers;	/* should be VFSIDCTL_VERS1 (below) */
+	fsid_t		vc_fsid;	/* fsid to operate on. */
+	void		*vc_ptr;	/* pointer to data structure. */
+	size_t		vc_len;		/* sizeof said structure. */
+	u_int32_t	vc_spare[12];	/* spare (must be zero). */
+};
+
+/* vfsidctl API version. */
+#define VFS_CTL_VERS1	0x01
+
+/*
+ * New style VFS sysctls, do not reuse/conflict with the namespace for
+ * private sysctls.
+ */
+#define VFS_CTL_STATFS	0x00010001	/* statfs */
+#define VFS_CTL_UMOUNT	0x00010002	/* unmount */
+#define VFS_CTL_QUERY	0x00010003	/* anything wrong? (vfsquery) */
+#define VFS_CTL_NEWADDR	0x00010004	/* reconnect to new address */
+#define VFS_CTL_TIMEO	0x00010005	/* set timeout for vfs notification */
+#define VFS_CTL_NOLOCKS	0x00010006	/* disable file locking */
+
+struct vfsquery {
+	u_int32_t	vq_flags;
+	u_int32_t	vq_spare[31];
+};
+
+/* vfsquery flags */
+#define VQ_NOTRESP	0x0001	/* server down */
+#define VQ_NEEDAUTH	0x0002	/* server bad auth */
+#define VQ_LOWDISK	0x0004	/* we're low on space */
+#define VQ_MOUNT	0x0008	/* new filesystem arrived */
+#define VQ_UNMOUNT	0x0010	/* filesystem has left */
+#define VQ_DEAD		0x0020	/* filesystem is dead, needs force unmount */
+#define VQ_ASSIST	0x0040	/* filesystem needs assistance from external
+				   program */
+#define VQ_NOTRESPLOCK	0x0080	/* server lockd down */
+#define VQ_FLAG0100	0x0100	/* placeholder */
+#define VQ_FLAG0200	0x0200	/* placeholder */
+#define VQ_FLAG0400	0x0400	/* placeholder */
+#define VQ_FLAG0800	0x0800	/* placeholder */
+#define VQ_FLAG1000	0x1000	/* placeholder */
+#define VQ_FLAG2000	0x2000	/* placeholder */
+#define VQ_FLAG4000	0x4000	/* placeholder */
+#define VQ_FLAG8000	0x8000	/* placeholder */
+
+#ifdef _KERNEL
+/* Point a sysctl request at a vfsidctl's data. */
+#define VCTLTOREQ(vc, req)						\
+	do {								\
+		(req)->newptr = (vc)->vc_ptr;				\
+		(req)->newlen = (vc)->vc_len;				\
+		(req)->newidx = 0;					\
+	} while (0)
+#endif
+
 struct iovec;
 struct uio;
 
@@ -397,6 +453,7 @@ extern struct vfsconf *vfsconf;	/* head of list of filesystem types */
  */
 struct mount_args;
 struct nameidata;
+struct sysctl_req;
 
 typedef int vfs_mount_t(struct mount *mp, char *path, caddr_t data,
 			struct nameidata *ndp, struct thread *td);
@@ -422,6 +479,7 @@ typedef	int vfs_extattrctl_t(struct mount *mp, int cmd,
 		    const char *attrname, struct thread *td);
 typedef	int vfs_nmount_t(struct mount *mp, struct nameidata *ndp,
 		    struct thread *td);
+typedef int vfs_sysctl_t(struct mount *mp, struct sysctl_req *req);
 
 struct vfsops {
 	vfs_mount_t		*vfs_mount;
@@ -440,6 +498,7 @@ struct vfsops {
 	vfs_extattrctl_t	*vfs_extattrctl;
 	/* Additions below are not binary compatible with 5.0 and below. */
 	vfs_nmount_t		*vfs_nmount;
+	vfs_sysctl_t		*vfs_sysctl;
 };
 
 #define VFS_NMOUNT(MP, NDP, P)    (*(MP)->mnt_op->vfs_nmount)(MP, NDP, P)
@@ -460,6 +519,9 @@ struct vfsops {
 	(*(MP)->mnt_op->vfs_checkexp)(MP, NAM, EXFLG, CRED)
 #define VFS_EXTATTRCTL(MP, C, FN, NS, N, P) \
 	(*(MP)->mnt_op->vfs_extattrctl)(MP, C, FN, NS, N, P)
+#define VFS_SYSCTL(MP, REQ) \
+    	((MP) == NULL ? ENOTSUP : \
+	 (*(MP)->mnt_op->vfs_sysctl)(MP, REQ))
 
 #include <sys/module.h>
 
@@ -486,6 +548,7 @@ extern	char *mountrootfsname;
 int	dounmount(struct mount *, int, struct thread *);
 int	kernel_mount(struct iovec *, u_int, int);
 int	kernel_vmount(int flags, ...);
+void	vfs_event_signal(fsid_t *, u_int32_t, void *);
 int	vfs_getopt(struct vfsoptlist *, const char *, void **, int *);
 int	vfs_copyopt(struct vfsoptlist *, const char *, void *, int);
 int	vfs_mount(struct thread *, const char *, char *, int, void *);