r14877: added support for the kernel inotify mechanism. This passes basic

tests, but still needs some more work to ensure we correctly cope with
events that may generate both a system inotify event and a internal
notify event. The system inotify events won't handle recursion, and
don't understand things like streams.

This also adds the ntvfs/sysdep/ directory, which is meant for system
dependent code that is not tied to a particular ntvfs backend. The
inotify code is a good example of that.
(This used to be commit eadadbb44adb3c4081d6ff1d85a9b850a0227059)

10 files changed, 587 insertions, 49 deletions

diff --git a/source4/configure.in b/source4/configure.in
index caf0787179..a4df9daba5 100644
--- a/source4/configure.in
+++ b/source4/configure.in
@@ -42,6 +42,7 @@ sinclude(lib/socket_wrapper/config.m4)
 sinclude(web_server/config.m4)
 sinclude(auth/config.m4)
 sinclude(kdc/config.m4)
+sinclude(ntvfs/sysdep/config.m4)
 
 AC_ARG_ENABLE(dso,
 [  --enable-dso 		Enable building internal libraries as DSO's (experimental)],
diff --git a/source4/ntvfs/common/notify.c b/source4/ntvfs/common/notify.c
index dd39aca095..595a0f6566 100644
--- a/source4/ntvfs/common/notify.c
+++ b/source4/ntvfs/common/notify.c
@@ -33,6 +33,7 @@
 #include "lib/messaging/irpc.h"
 #include "librpc/gen_ndr/ndr_notify.h"
 #include "dlinklist.h"
+#include "ntvfs/sysdep/sys_notify.h"
 
 struct notify_context {
 	struct tdb_wrap *w;
@@ -41,6 +42,7 @@ struct notify_context {
 	struct notify_list *list;
 	struct notify_array *array;
 	int seqnum;
+	struct sys_notify_context *sys_notify_ctx;
 };
 
 
@@ -48,6 +50,7 @@ struct notify_list {
 	struct notify_list *next, *prev;
 	void *private;
 	void (*callback)(void *, const struct notify_event *);
+	void *sys_notify_handle;
 };
 
 #define NOTIFY_KEY "notify array"
@@ -73,7 +76,8 @@ static int notify_destructor(void *p)
   via internal messages
 */
 struct notify_context *notify_init(TALLOC_CTX *mem_ctx, uint32_t server, 
-				   struct messaging_context *messaging_ctx)
+				   struct messaging_context *messaging_ctx,
+				   struct event_context *ev)
 {
 	char *path;
 	struct notify_context *notify;
@@ -106,6 +110,8 @@ struct notify_context *notify_init(TALLOC_CTX *mem_ctx, uint32_t server,
 	messaging_register(notify->messaging_ctx, notify, 
 			   MSG_PVFS_NOTIFY, notify_handler);
 
+	notify->sys_notify_ctx = sys_notify_init(-1, notify, ev);
+
 	return notify;
 }
 
@@ -166,6 +172,14 @@ static NTSTATUS notify_load(struct notify_context *notify)
 	return status;
 }
 
+/*
+  compare notify entries for sorting
+*/
+static int notify_compare(const void *p1, const void *p2)
+{
+	const struct notify_entry *e1 = p1, *e2 = p2;
+	return strcmp(e1->path, e2->path);
+}
 
 /*
   save the notify array
@@ -186,6 +200,11 @@ static NTSTATUS notify_save(struct notify_context *notify)
 		return NT_STATUS_OK;
 	}
 
+	if (notify->array->num_entries > 1) {
+		qsort(notify->array->entries, notify->array->num_entries, 
+		      sizeof(struct notify_entry), notify_compare);
+	}
+
 	tmp_ctx = talloc_new(notify);
 
 	status = ndr_push_struct_blob(&blob, tmp_ctx, notify->array, 
@@ -238,6 +257,17 @@ static void notify_handler(struct messaging_context *msg_ctx, void *private,
 }
 
 /*
+  callback from sys_notify telling us about changes from the OS
+*/
+static void sys_notify_callback(struct sys_notify_context *ctx, 
+				void *ptr, struct notify_event *ev)
+{
+	struct notify_list *listel = talloc_get_type(ptr, struct notify_list);
+	ev->private = listel;
+	listel->callback(listel->private, ev);
+}
+
+/*
   add a notify watch. This is called when a notify is first setup on a open
   directory handle.
 */
@@ -274,33 +304,42 @@ NTSTATUS notify_add(struct notify_context *notify, struct notify_entry *e,
 		path = talloc_strndup(notify, e->path, len-2);
 	}
 
-	notify->array->entries[notify->array->num_entries] = *e;
-	notify->array->entries[notify->array->num_entries].private = private;
-	notify->array->entries[notify->array->num_entries].server = notify->server;
+	listel = talloc_zero(notify, struct notify_list);
+	NT_STATUS_HAVE_NO_MEMORY(listel);
 
-	if (path) {
-		notify->array->entries[notify->array->num_entries].path = path;
-	}
+	listel->private = private;
+	listel->callback = callback;
+	DLIST_ADD(notify->list, listel);
 
-	notify->array->num_entries++;
+	/* ignore failures from sys_notify */
+	status = sys_notify_watch(notify->sys_notify_ctx, e->path, e->filter, 
+				  sys_notify_callback, listel, 
+				  &listel->sys_notify_handle);
+	if (NT_STATUS_IS_OK(status)) {
+		talloc_steal(listel, listel->sys_notify_handle);
+		notify_unlock(notify);
+	} else {
+		notify->array->entries[notify->array->num_entries] = *e;
+		notify->array->entries[notify->array->num_entries].private = private;
+		notify->array->entries[notify->array->num_entries].server = notify->server;
 
-	status = notify_save(notify);
+		if (path) {
+			notify->array->entries[notify->array->num_entries].path = path;
+		}
 
-	notify_unlock(notify);
+		notify->array->num_entries++;
 
-	NT_STATUS_NOT_OK_RETURN(status);
+		status = notify_save(notify);
+
+		notify_unlock(notify);
+
+		NT_STATUS_NOT_OK_RETURN(status);
+	}
 
 	if (path) {
 		talloc_free(path);
 	}
 
-	listel = talloc(notify, struct notify_list);
-	NT_STATUS_HAVE_NO_MEMORY(listel);
-
-	listel->private = private;
-	listel->callback = callback;
-	DLIST_ADD(notify->list, listel);
-
 	return status;
 }
 
@@ -323,6 +362,8 @@ NTSTATUS notify_remove(struct notify_context *notify, void *private)
 		return NT_STATUS_OBJECT_NAME_NOT_FOUND;
 	}
 
+	talloc_free(listel);
+
 	status = notify_lock(notify);
 	NT_STATUS_NOT_OK_RETURN(status);
 
@@ -398,6 +439,35 @@ static NTSTATUS notify_remove_all(struct notify_context *notify)
 
 
 /*
+  send a notify message to another messaging server
+*/
+static void notify_send(struct notify_context *notify, struct notify_entry *e,
+			const char *path, uint32_t action)
+{
+	struct notify_event ev;
+	DATA_BLOB data;
+	NTSTATUS status;
+	TALLOC_CTX *tmp_ctx;
+
+	ev.action = action;
+	ev.path = path;
+	ev.private = e->private;
+
+	tmp_ctx = talloc_new(notify);
+
+	status = ndr_push_struct_blob(&data, tmp_ctx, &ev, 
+				      (ndr_push_flags_fn_t)ndr_push_notify_event);
+	if (!NT_STATUS_IS_OK(status)) {
+		talloc_free(tmp_ctx);
+		return;
+	}
+
+	status = messaging_send(notify->messaging_ctx, e->server, 
+				MSG_PVFS_NOTIFY, &data);
+	talloc_free(tmp_ctx);
+}
+
+/*
   see if a notify event matches
 */
 static BOOL notify_match(struct notify_context *notify, struct notify_entry *e,
@@ -430,35 +500,6 @@ static BOOL notify_match(struct notify_context *notify, struct notify_entry *e,
 
 
 /*
-  send a notify message to another messaging server
-*/
-static void notify_send(struct notify_context *notify, struct notify_entry *e,
-			const char *path, uint32_t action)
-{
-	struct notify_event ev;
-	DATA_BLOB data;
-	NTSTATUS status;
-	TALLOC_CTX *tmp_ctx;
-
-	ev.action = action;
-	ev.path = path;
-	ev.private = e->private;
-
-	tmp_ctx = talloc_new(notify);
-
-	status = ndr_push_struct_blob(&data, tmp_ctx, &ev, 
-				      (ndr_push_flags_fn_t)ndr_push_notify_event);
-	if (!NT_STATUS_IS_OK(status)) {
-		talloc_free(tmp_ctx);
-		return;
-	}
-
-	status = messaging_send(notify->messaging_ctx, e->server, 
-				MSG_PVFS_NOTIFY, &data);
-	talloc_free(tmp_ctx);
-}
-
-/*
   trigger a notify message for anyone waiting on a matching event
 */
 void notify_trigger(struct notify_context *notify,
@@ -472,7 +513,7 @@ void notify_trigger(struct notify_context *notify,
 		return;
 	}
 
-	/* this needs to be changed to a log(n) search */
+	/* TODO: this needs to be changed to a log(n) search */
 	for (i=0;i<notify->array->num_entries;i++) {
 		if (notify_match(notify, &notify->array->entries[i], path, filter)) {
 			notify_send(notify, &notify->array->entries[i], 
diff --git a/source4/ntvfs/config.mk b/source4/ntvfs/config.mk
index f17097e356..2a35bd5cb3 100644
--- a/source4/ntvfs/config.mk
+++ b/source4/ntvfs/config.mk
@@ -2,6 +2,7 @@
 include posix/config.mk
 include common/config.mk
 include unixuid/config.mk
+include sysdep/config.mk
 
 ################################################
 # Start MODULE ntvfs_cifs
diff --git a/source4/ntvfs/posix/vfs_posix.c b/source4/ntvfs/posix/vfs_posix.c
index d161dac5a4..c279350e2f 100644
--- a/source4/ntvfs/posix/vfs_posix.c
+++ b/source4/ntvfs/posix/vfs_posix.c
@@ -30,6 +30,7 @@
 #include "lib/tdb/include/tdb.h"
 #include "db_wrap.h"
 #include "libcli/security/security.h"
+#include "lib/events/events.h"
 
 
 /*
@@ -186,7 +187,8 @@ static NTSTATUS pvfs_connect(struct ntvfs_module_context *ntvfs,
 
 	pvfs->notify_context = notify_init(pvfs, 
 					   pvfs->ntvfs->ctx->server_id,  
-					   pvfs->ntvfs->ctx->msg_ctx);
+					   pvfs->ntvfs->ctx->msg_ctx, 
+					   event_context_find(pvfs));
 	if (pvfs->notify_context == NULL) {
 		return NT_STATUS_INTERNAL_DB_CORRUPTION;
 	}
diff --git a/source4/ntvfs/sysdep/README b/source4/ntvfs/sysdep/README
new file mode 100644
index 0000000000..a2a8f57c28
--- /dev/null
+++ b/source4/ntvfs/sysdep/README
@@ -0,0 +1,5 @@
+This directory contains OS depdendent interfaces to facilities that
+are only available on a few of our target systems, and require
+substantial code to abstract.
+
+
diff --git a/source4/ntvfs/sysdep/config.m4 b/source4/ntvfs/sysdep/config.m4
new file mode 100644
index 0000000000..f67a3bdace
--- /dev/null
+++ b/source4/ntvfs/sysdep/config.m4
@@ -0,0 +1,7 @@
+AC_CHECK_HEADERS(linux/inotify.h asm/unistd.h)
+AC_CHECK_FUNC(inotify_init)
+
+SMB_ENABLE(ntvfs_inotify, NO)
+if test x"$ac_cv_header_linux_inotify_h" = x"yes"; then
+    SMB_ENABLE(ntvfs_inotify, YES)
+fi
diff --git a/source4/ntvfs/sysdep/config.mk b/source4/ntvfs/sysdep/config.mk
new file mode 100644
index 0000000000..3bcebb5c0e
--- /dev/null
+++ b/source4/ntvfs/sysdep/config.mk
@@ -0,0 +1,20 @@
+################################################
+# Start MODULE ntvfs_sys_notify
+[MODULE::ntvfs_sys_notify]
+SUBSYSTEM = ntvfs
+OBJ_FILES = \
+		sys_notify.o
+# End MODULE ntvfs_sys_notify
+################################################
+
+
+################################################
+# Start MODULE ntvfs_inotify
+[MODULE::ntvfs_inotify]
+SUBSYSTEM = ntvfs
+INIT_FUNCTION = ntvfs_inotify_init
+OBJ_FILES = \
+		inotify.o
+# End MODULE ntvfs_inotify
+################################################
+
diff --git a/source4/ntvfs/sysdep/inotify.c b/source4/ntvfs/sysdep/inotify.c
new file mode 100644
index 0000000000..31c408d112
--- /dev/null
+++ b/source4/ntvfs/sysdep/inotify.c
@@ -0,0 +1,313 @@
+/* 
+   Unix SMB/CIFS implementation.
+
+   Copyright (C) Andrew Tridgell 2006
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+/*
+  notify implementation using inotify
+*/
+
+#include "includes.h"
+#include "system/filesys.h"
+#include "ntvfs/sysdep/sys_notify.h"
+#include "lib/events/events.h"
+#include "smb.h"
+#include "dlinklist.h"
+
+#include <linux/inotify.h>
+#include <asm/unistd.h>
+
+#ifndef HAVE_INOTIFY_INIT
+/*
+  glibc doesn't define these functions yet (as of March 2006)
+*/
+static int inotify_init(void)
+{
+	return syscall(__NR_inotify_init);
+}
+
+static int inotify_add_watch(int fd, const char *path, __u32 mask)
+{
+	return syscall(__NR_inotify_add_watch, fd, path, mask);
+}
+
+static int inotify_rm_watch(int fd, int wd)
+{
+	return syscall(__NR_inotify_rm_watch, fd, wd);
+}
+#endif
+
+
+/* older glibc headers don't have these defines either */
+#ifndef IN_ONLYDIR
+#define IN_ONLYDIR 0x01000000
+#endif
+#ifndef IN_MASK_ADD
+#define IN_MASK_ADD 0x20000000
+#endif
+
+struct inotify_private {
+	struct sys_notify_context *ctx;
+	int fd;
+	struct watch_context *watches;
+};
+
+struct watch_context {
+	struct watch_context *next, *prev;
+	struct inotify_private *in;
+	int wd;
+	sys_notify_callback_t callback;
+	void *private;
+	uint32_t mask;
+};
+
+
+/*
+  destroy the inotify private context
+*/
+static int inotify_destructor(void *ptr)
+{
+	struct inotify_private *in = talloc_get_type(ptr, struct inotify_private);
+	close(in->fd);
+	return 0;
+}
+
+
+/*
+  dispatch one inotify event
+*/
+static void inotify_dispatch(struct inotify_private *in, struct inotify_event *e)
+{
+	struct watch_context *w;
+	struct notify_event ne;
+
+	/* ignore extraneous events, such as unmount and IN_IGNORED events */
+	if ((e->mask & (IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO)) == 0) {
+		return;
+	}
+
+	/* map the inotify mask to a action */
+	if (e->mask & IN_CREATE) {
+		ne.action = NOTIFY_ACTION_ADDED;
+	} else if (e->mask & IN_DELETE) {
+		ne.action = NOTIFY_ACTION_REMOVED;
+	} else {
+		ne.action = NOTIFY_ACTION_MODIFIED;
+	}
+	ne.path = e->name;
+
+	/* find any watches that have this watch descriptor */
+	for (w=in->watches;w;w=w->next) {
+		/* checking the mask copes with multiple watches */
+		if (w->wd == e->wd && (e->mask & w->mask) != 0) {
+			w->callback(in->ctx, w->private, &ne);
+		}
+	}
+}
+
+/*
+  called when the kernel has some events for us
+*/
+static void inotify_handler(struct event_context *ev, struct fd_event *fde,
+			    uint16_t flags, void *private)
+{
+	struct inotify_private *in = talloc_get_type(private, struct inotify_private);
+	int bufsize = 0;
+	struct inotify_event *e0, *e;
+
+	/*
+	  we must use FIONREAD as we cannot predict the length of the
+	  filenames, and thus can't know how much to allocate
+	  otherwise
+	*/
+	if (ioctl(in->fd, FIONREAD, &bufsize) != 0 || 
+	    bufsize == 0) {
+		DEBUG(0,("No data on inotify fd?!\n"));
+		return;
+	}
+
+	e0 = e = talloc_size(in, bufsize);
+	if (e == NULL) return;
+
+	if (read(in->fd, e0, bufsize) != bufsize) {
+		DEBUG(0,("Failed to read all inotify data\n"));
+		talloc_free(e0);
+		return;
+	}
+
+	/* we can get more than one event in the buffer */
+	while (bufsize >= sizeof(*e)) {
+		inotify_dispatch(in, e);
+		bufsize -= e->len + sizeof(*e);
+		e = (struct inotify_event *)(e->len + sizeof(*e) + (char *)e);
+	}
+
+	talloc_free(e0);
+}
+
+/*
+  setup the inotify handle - called the first time a watch is added on
+  this context
+*/
+static NTSTATUS inotify_setup(struct sys_notify_context *ctx)
+{
+	struct inotify_private *in;
+
+	in = talloc(ctx, struct inotify_private);
+	NT_STATUS_HAVE_NO_MEMORY(in);
+	in->fd = inotify_init();
+	if (in->fd == -1) {
+		DEBUG(0,("Failed to init inotify - %s\n", strerror(errno)));
+		talloc_free(in);
+		return map_nt_error_from_unix(errno);
+	}
+	in->ctx = ctx;
+	in->watches = NULL;
+
+	ctx->private = in;
+	talloc_set_destructor(in, inotify_destructor);
+
+	/* add a event waiting for the inotify fd to be readable */
+	event_add_fd(ctx->ev, in, in->fd, EVENT_FD_READ, inotify_handler, in);
+	
+	return NT_STATUS_OK;
+}
+
+
+/*
+  map from a change notify mask to a inotify mask. Approximate only :(
+*/
+static const struct {
+	uint32_t notify_mask;
+	uint32_t inotify_mask;
+} inotify_mapping[] = {
+	{FILE_NOTIFY_CHANGE_FILE_NAME,  IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO},
+	{FILE_NOTIFY_CHANGE_ATTRIBUTES, IN_ATTRIB},
+	{FILE_NOTIFY_CHANGE_SIZE,       IN_MODIFY},
+	{FILE_NOTIFY_CHANGE_LAST_WRITE, IN_ATTRIB},
+	{FILE_NOTIFY_CHANGE_EA,         IN_ATTRIB},
+	{FILE_NOTIFY_CHANGE_SECURITY,   IN_ATTRIB}
+};
+
+static uint32_t inotify_map(uint32_t mask)
+{
+	int i;
+	uint32_t out=0;
+	for (i=0;i<ARRAY_SIZE(inotify_mapping);i++) {
+		if (inotify_mapping[i].notify_mask & mask) {
+			out |= inotify_mapping[i].inotify_mask;
+		}
+	}
+	return out;
+}
+
+/*
+  destroy a watch
+*/
+static int watch_destructor(void *ptr)
+{
+	struct watch_context *w = talloc_get_type(ptr, struct watch_context);
+	struct inotify_private *in = w->in;
+	int wd = w->wd;
+	DLIST_REMOVE(w->in->watches, w);
+
+	/* only rm the watch if its the last one with this wd */
+	for (w=in->watches;w;w=w->next) {
+		if (w->wd == wd) break;
+	}
+	if (w == NULL) {
+		inotify_rm_watch(in->fd, wd);
+	}
+	return 0;
+}
+
+
+/*
+  add a watch. The watch is removed when the caller calls
+  talloc_free() on handle
+*/
+static NTSTATUS inotify_watch(struct sys_notify_context *ctx, const char *dirpath,
+			      uint32_t filter, sys_notify_callback_t callback,
+			      void *private, void **handle)
+{
+	struct inotify_private *in;
+	int wd;
+	uint32_t mask;
+	struct watch_context *w;
+
+	/* maybe setup the inotify fd */
+	if (ctx->private == NULL) {
+		NTSTATUS status;
+		status = inotify_setup(ctx);
+		NT_STATUS_NOT_OK_RETURN(status);
+	}
+
+	in = talloc_get_type(ctx->private, struct inotify_private);
+
+	mask = inotify_map(filter);
+	if (mask == 0) {
+		/* this filter can't be handled by inotify */
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	/* using IN_MASK_ADD allows us to cope with inotify() returning the same
+	   watch descriptor for muliple watches on the same path */
+	mask |= (IN_MASK_ADD | IN_ONLYDIR);
+
+	/* get a new watch descriptor for this path */
+	wd = inotify_add_watch(in->fd, dirpath, mask);
+	if (wd == -1) {
+		return map_nt_error_from_unix(errno);
+	}
+
+	w = talloc(in, struct watch_context);
+	if (w == NULL) {
+		inotify_rm_watch(in->fd, wd);
+		return NT_STATUS_NO_MEMORY;
+	}
+
+	w->in = in;
+	w->wd = wd;
+	w->callback = callback;
+	w->private = private;
+	w->mask = mask;
+
+	(*handle) = w;
+
+	DLIST_ADD(in->watches, w);
+
+	/* the caller frees the handle to stop watching */
+	talloc_set_destructor(w, watch_destructor);
+	
+	return NT_STATUS_OK;
+}
+
+
+static struct sys_notify_backend inotify = {
+	.name = "inotify",
+	.notify_watch = inotify_watch
+};
+
+/*
+  initialialise the inotify module
+ */
+NTSTATUS ntvfs_inotify_init(void)
+{
+	/* register ourselves as a system inotify module */
+	return sys_notify_register(&inotify);
+}
diff --git a/source4/ntvfs/sysdep/sys_notify.c b/source4/ntvfs/sysdep/sys_notify.c
new file mode 100644
index 0000000000..aedfd2a7de
--- /dev/null
+++ b/source4/ntvfs/sysdep/sys_notify.c
@@ -0,0 +1,96 @@
+/* 
+   Unix SMB/CIFS implementation.
+
+   Copyright (C) Andrew Tridgell 2006
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+/*
+  abstract the various kernel interfaces to change notify into a
+  single Samba friendly interface
+*/
+
+#include "includes.h"
+#include "system/filesys.h"
+#include "ntvfs/sysdep/sys_notify.h"
+#include "lib/events/events.h"
+#include "dlinklist.h"
+
+/* list of registered backends */
+static struct sys_notify_backend *backends;
+
+
+/*
+  initialise a system change notify backend
+*/
+struct sys_notify_context *sys_notify_init(int snum,
+					   TALLOC_CTX *mem_ctx, 
+					   struct event_context *ev)
+{
+	struct sys_notify_context *ctx;
+	const char *bname;
+	struct sys_notify_backend *b;
+
+	if (backends == NULL) {
+		return NULL;
+	}
+
+	if (ev == NULL) {
+		ev = event_context_find(mem_ctx);
+	}
+
+	ctx = talloc_zero(mem_ctx, struct sys_notify_context);
+	if (ctx == NULL) {
+		return NULL;
+	}
+
+	ctx->ev = ev;
+
+	bname = lp_parm_string(snum, "notify", "backend");
+	if (bname == NULL) {
+		bname = backends->name;
+	}
+
+	for (b=backends;b;b=b->next) {
+		if (strcasecmp(b->name, bname) == 0) break;
+	}
+
+	if (b != NULL) {
+		ctx->name = b->name;
+		ctx->notify_watch = b->notify_watch;
+	}
+
+	return ctx;
+}
+
+/*
+  add a watch
+*/
+NTSTATUS sys_notify_watch(struct sys_notify_context *ctx, const char *dirpath,
+			  uint32_t filter, sys_notify_callback_t callback,
+			  void *private, void **handle)
+{
+	return ctx->notify_watch(ctx, dirpath, filter, callback, private, handle);
+}
+
+/*
+  register a notify backend
+*/
+NTSTATUS sys_notify_register(struct sys_notify_backend *backend)
+{
+	DLIST_ADD(backends, backend);
+	return NT_STATUS_OK;
+}
diff --git a/source4/ntvfs/sysdep/sys_notify.h b/source4/ntvfs/sysdep/sys_notify.h
new file mode 100644
index 0000000000..9ad5ed7555
--- /dev/null
+++ b/source4/ntvfs/sysdep/sys_notify.h
@@ -0,0 +1,52 @@
+/* 
+   Unix SMB/CIFS implementation.
+
+   Copyright (C) Andrew Tridgell 2006
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include "librpc/gen_ndr/notify.h"
+
+struct sys_notify_context;
+
+typedef void (*sys_notify_callback_t)(struct sys_notify_context *, 
+				      void *, struct notify_event *ev);
+
+struct sys_notify_context {
+	struct event_context *ev;
+	void *private; /* for use of backend */
+	NTSTATUS (*notify_watch)(struct sys_notify_context *ctx, const char *dirpath,
+				 uint32_t filter, sys_notify_callback_t callback,
+				 void *private, void **handle);
+	const char *name;
+};
+
+struct sys_notify_backend {
+	struct sys_notify_backend *next, *prev;
+	const char *name;
+	NTSTATUS (*notify_watch)(struct sys_notify_context *ctx, const char *dirpath,
+				 uint32_t filter, sys_notify_callback_t callback,
+				 void *private, void **handle);
+};
+
+NTSTATUS sys_notify_register(struct sys_notify_backend *backend);
+struct sys_notify_context *sys_notify_init(int snum,
+					   TALLOC_CTX *mem_ctx, 
+					   struct event_context *ev);
+NTSTATUS sys_notify_watch(struct sys_notify_context *ctx, const char *dirpath,
+			  uint32_t filter, sys_notify_callback_t callback,
+			  void *private, void **handle);
+