totally rewrote the async signal, notification and oplock notification

handling in Samba. This was needed due to several limitations and
races in the previous code - as a side effect the new code is much
cleaner :)

in summary:

- changed sys_select() to avoid a signal/select race condition. It is a
  rare race but once we have signals doing notification and oplocks it
  is important.

- changed our main processing loop to take advantage of the new
  sys_select semantics

- split the notify code into implementaion dependent and general
  parts. Added the following structure that defines an implementation:

struct cnotify_fns {
	void * (*register_notify)(connection_struct *conn, char *path, uint32 flags);
	BOOL (*check_notify)(connection_struct *conn, uint16 vuid, char *path, uint32 flags, void *data, time_t t);
	void (*remove_notify)(void *data);
};


then I wrote two implementations, one using hash/poll (like our old
code) and the other using the new Linux kernel change notify. It
should be easy to add other change notify implementations by creating
a sructure of the above type.

- fixed a bug in change notify where we were returning the wrong error
  code.

- rewrote the core change notify code to be much simpler

- moved to real-time signals for leases and change notify

Amazingly, it all seems to work. I was very surprised!
(This used to be commit 44766c39e0027c762bee8b33b12c621c109a3267)

1 files changed, 170 insertions, 0 deletions

diff --git a/source3/smbd/notify_kernel.c b/source3/smbd/notify_kernel.c
new file mode 100644
index 0000000000..7732bc646f
--- /dev/null
+++ b/source3/smbd/notify_kernel.c
@@ -0,0 +1,170 @@
+#define OLD_NTDOMAIN 1
+/*
+   Unix SMB/Netbios implementation.
+   Version 3.0
+   change notify handling - linux kernel based implementation
+   Copyright (C) Andrew Tridgell 2000
+
+   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 "includes.h"
+
+#if HAVE_KERNEL_CHANGE_NOTIFY
+
+extern int DEBUGLEVEL;
+static int fd_pending;
+static unsigned signals_received;
+static unsigned signals_processed;
+
+#ifndef DN_ACCESS
+#define DN_ACCESS       0x00000001      /* File accessed in directory */
+#define DN_MODIFY       0x00000002      /* File modified in directory */
+#define DN_CREATE       0x00000004      /* File created in directory */
+#define DN_DELETE       0x00000008      /* File removed from directory */
+#define DN_RENAME       0x00000010      /* File renamed in directory */
+#define DN_MULTISHOT    0x80000000      /* Don't remove notifier */
+#endif
+
+
+#ifndef RT_SIGNAL_NOTIFY
+#define RT_SIGNAL_NOTIFY 34
+#endif
+
+/****************************************************************************
+ This is the structure to keep the information needed to
+ determine if a directory has changed.
+*****************************************************************************/
+struct change_data {
+	int directory_handle;
+};
+
+/****************************************************************************
+the signal handler for change notify
+*****************************************************************************/
+static void signal_handler(int signal, siginfo_t *info, void *unused)
+{
+	BlockSignals(True, signal);
+	fd_pending = info->si_fd;
+	signals_received++;
+	sys_select_signal();
+}
+
+
+
+/****************************************************************************
+check if a change notify should be issued 
+*****************************************************************************/
+static BOOL kernel_check_notify(connection_struct *conn, uint16 vuid, char *path, uint32 flags, void *datap, time_t t)
+{
+	struct change_data *data = (struct change_data *)datap;
+
+	if (data->directory_handle != fd_pending) return False;
+
+	close(fd_pending);
+	data->directory_handle = fd_pending = -1;
+	signals_processed++;
+	BlockSignals(False, RT_SIGNAL_NOTIFY);
+	return True;
+}
+
+/****************************************************************************
+remove a change notify data structure
+*****************************************************************************/
+static void kernel_remove_notify(void *datap)
+{
+	struct change_data *data = (struct change_data *)datap;
+	if (data->directory_handle != -1) {
+		if (data->directory_handle == fd_pending) {
+			data->directory_handle = fd_pending = -1;
+			signals_processed++;
+			BlockSignals(False, RT_SIGNAL_NOTIFY);
+		}
+		close(data->directory_handle);
+	}
+	free(data);
+}
+
+
+/****************************************************************************
+register a change notify request
+*****************************************************************************/
+static void *kernel_register_notify(connection_struct *conn, char *path, uint32 flags)
+{
+	struct change_data data;
+	int fd;
+	unsigned long kernel_flags;
+	
+	fd = dos_open(fsp->fsp_name, O_RDONLY, 0);
+
+	if (fd == -1) {
+		DEBUG(3,("Failed to open directory %s for change notify\n", fsp->fsp_name));
+		return NULL;
+	}
+
+	if (fcntl(fd, F_SETSIG, RT_SIGNAL_NOTIFY) == -1) {
+		DEBUG(3,("Failed to set signal handler for change notify\n"));
+		return NULL;
+	}
+
+	kernel_flags = 0;
+	if (flags & FILE_NOTIFY_CHANGE_FILE_NAME)   kernel_flags |= DN_RENAME;
+	if (flags & FILE_NOTIFY_CHANGE_DIR_NAME)    kernel_flags |= DN_RENAME;
+	if (flags & FILE_NOTIFY_CHANGE_ATTRIBUTES)  kernel_flags |= DN_MODIFY;
+	if (flags & FILE_NOTIFY_CHANGE_SIZE)        kernel_flags |= DN_MODIFY;
+	if (flags & FILE_NOTIFY_CHANGE_LAST_WRITE)  kernel_flags |= DN_MODIFY;
+	if (flags & FILE_NOTIFY_CHANGE_LAST_ACCESS) kernel_flags |= DN_ACCESS;
+	if (flags & FILE_NOTIFY_CHANGE_CREATION)    kernel_flags |= DN_CREATE;
+
+	if (fcntl(fd, F_NOTIFY, kernel_flags) == -1) {
+		DEBUG(3,("Failed to set async flag for change notify\n"));
+		return NULL;
+	}
+
+	data.directory_handle = fd;
+
+	return (void *)memdup(&data, sizeof(data));
+}
+
+
+/****************************************************************************
+setup kernel based change notify
+****************************************************************************/
+struct cnotify_fns *kernel_notify_init(void) 
+{
+	static struct cnotify_fns cnotify;
+        struct sigaction act;
+
+        act.sa_handler = NULL;
+        act.sa_sigaction = signal_handler;
+        act.sa_flags = SA_SIGINFO;
+        if (sigaction(RT_SIGNAL_NOTIFY, &act, NULL) != 0) {
+		DEBUG(0,("Failed to setup RT_SIGNAL_NOTIFY handler\n"));
+		return NULL;
+        }
+
+	cnotify.register_notify = kernel_register_notify;
+	cnotify.check_notify = kernel_check_notify;
+	cnotify.remove_notify = kernel_remove_notify;
+
+	return &cnotify;
+}
+
+
+#else
+ void notify_kernel_dummy(void) {}
+#endif /* HAVE_KERNEL_CHANGE_NOTIFY */
+
+#undef OLD_NTDOMAIN