Adding upstream version 2:4.20.0+dfsg.upstream/2%4.20.0+dfsg

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 757 insertions, 0 deletions

diff --git a/source3/modules/vfs_preopen.c b/source3/modules/vfs_preopen.c
new file mode 100644
index 0000000..d1327f6
--- /dev/null
+++ b/source3/modules/vfs_preopen.c
@@ -0,0 +1,757 @@
+/*
+ * Force a readahead of files by opening them and reading the first bytes
+ *
+ * Copyright (C) Volker Lendecke 2008
+ *
+ * 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"
+#include "system/filesys.h"
+#include "smbd/smbd.h"
+#include "lib/util/sys_rw.h"
+#include "lib/util/sys_rw_data.h"
+#include "lib/util/smb_strtox.h"
+#include "lib/util_matching.h"
+#include "lib/global_contexts.h"
+
+static int vfs_preopen_debug_level = DBGC_VFS;
+
+#undef DBGC_CLASS
+#define DBGC_CLASS vfs_preopen_debug_level
+
+#define PREOPEN_MAX_DIGITS 19
+#define PREOPEN_MAX_NUMBER (uint64_t)9999999999999999999ULL
+
+struct preopen_state;
+
+struct preopen_helper {
+	struct preopen_state *state;
+	struct tevent_fd *fde;
+	pid_t pid;
+	int fd;
+	bool busy;
+};
+
+struct preopen_state {
+	int num_helpers;
+	struct preopen_helper *helpers;
+
+	size_t to_read;		/* How many bytes to read in children? */
+	int queue_max;
+
+	int queue_dbglvl;       /* DBGLVL_DEBUG by default */
+	int nomatch_dbglvl;     /* DBGLVL_INFO by default */
+	int match_dbglvl;       /* DBGLVL_INFO by default */
+	int reset_dbglvl;       /* DBGLVL_INFO by default */
+	int nodigits_dbglvl;    /* DBGLVL_WARNING by default */
+	int founddigits_dbglvl; /* DBGLVL_NOTICE by default */
+	int push_dbglvl;        /* DBGLVL_NOTICE by default */
+
+	char *template_fname;	/* Filename to be sent to children */
+	size_t number_start;	/* start offset into "template_fname" */
+	int num_digits;		/* How many digits is the number long? */
+
+	uint64_t fnum_sent;	/* last fname sent to children */
+
+	uint64_t fnum_queue_end;/* last fname to be sent, based on
+				 * last open call + preopen:queuelen
+				 */
+
+	struct samba_path_matching *preopen_names;
+	ssize_t last_match_idx; /* remember the last match */
+};
+
+static void preopen_helper_destroy(struct preopen_helper *c)
+{
+	int status;
+	TALLOC_FREE(c->fde);
+	close(c->fd);
+	c->fd = -1;
+	kill(c->pid, SIGKILL);
+	waitpid(c->pid, &status, 0);
+	c->busy = true;
+}
+
+static void preopen_queue_run(struct preopen_state *state)
+{
+	char *pdelimiter;
+	char delimiter;
+
+	DBG_PREFIX(state->queue_dbglvl, ("START: "
+		   "last_fname[%s] start_offset=%zu num_digits=%d "
+		   "last_pushed_num=%"PRIu64" queue_end_num=%"PRIu64" num_helpers=%d\n",
+		   state->template_fname,
+		   state->number_start,
+		   state->num_digits,
+		   state->fnum_sent,
+		   state->fnum_queue_end,
+		   state->num_helpers));
+
+	pdelimiter = state->template_fname + state->number_start
+		+ state->num_digits;
+	delimiter = *pdelimiter;
+
+	while (state->fnum_sent < state->fnum_queue_end) {
+
+		ssize_t written;
+		size_t to_write;
+		int helper;
+
+		for (helper=0; helper<state->num_helpers; helper++) {
+			if (state->helpers[helper].busy) {
+				continue;
+			}
+			break;
+		}
+		if (helper == state->num_helpers) {
+			/* everyone is busy */
+			DBG_PREFIX(state->queue_dbglvl, ("BUSY: "
+				   "template_fname[%s] start_offset=%zu num_digits=%d "
+				   "last_pushed_num=%"PRIu64" queue_end_num=%"PRIu64"\n",
+				   state->template_fname,
+				   state->number_start,
+				   state->num_digits,
+				   state->fnum_sent,
+				   state->fnum_queue_end));
+			return;
+		}
+
+		snprintf(state->template_fname + state->number_start,
+			 state->num_digits + 1,
+			 "%.*llu", state->num_digits,
+			 (long long unsigned int)(state->fnum_sent + 1));
+		*pdelimiter = delimiter;
+
+		DBG_PREFIX(state->push_dbglvl, (
+			   "PUSH: fullpath[%s] to helper(idx=%d)\n",
+			   state->template_fname, helper));
+
+		to_write = talloc_get_size(state->template_fname);
+		written = write_data(state->helpers[helper].fd,
+				     state->template_fname, to_write);
+		state->helpers[helper].busy = true;
+
+		if (written != to_write) {
+			preopen_helper_destroy(&state->helpers[helper]);
+		}
+		state->fnum_sent += 1;
+	}
+	DBG_PREFIX(state->queue_dbglvl, ("END: "
+		   "template_fname[%s] start_offset=%zu num_digits=%d "
+		   "last_pushed_num=%"PRIu64" queue_end_num=%"PRIu64"\n",
+		   state->template_fname,
+		   state->number_start,
+		   state->num_digits,
+		   state->fnum_sent,
+		   state->fnum_queue_end));
+}
+
+static void preopen_helper_readable(struct tevent_context *ev,
+				    struct tevent_fd *fde, uint16_t flags,
+				    void *priv)
+{
+	struct preopen_helper *helper = (struct preopen_helper *)priv;
+	struct preopen_state *state = helper->state;
+	ssize_t nread;
+	char c;
+
+	if ((flags & TEVENT_FD_READ) == 0) {
+		return;
+	}
+
+	nread = read(helper->fd, &c, 1);
+	if (nread <= 0) {
+		preopen_helper_destroy(helper);
+		return;
+	}
+
+	helper->busy = false;
+
+	DBG_PREFIX(state->queue_dbglvl, ("BEFORE: preopen_queue_run\n"));
+	preopen_queue_run(state);
+	DBG_PREFIX(state->queue_dbglvl, ("AFTER: preopen_queue_run\n"));
+}
+
+static int preopen_helpers_destructor(struct preopen_state *c)
+{
+	int i;
+
+	for (i=0; i<c->num_helpers; i++) {
+		if (c->helpers[i].fd == -1) {
+			continue;
+		}
+		preopen_helper_destroy(&c->helpers[i]);
+	}
+
+	return 0;
+}
+
+static bool preopen_helper_open_one(int sock_fd, char **pnamebuf,
+				    size_t to_read, void *filebuf)
+{
+	char *namebuf = *pnamebuf;
+	ssize_t nread;
+	char c = 0;
+	int fd;
+
+	nread = 0;
+
+	do {
+		ssize_t thistime;
+
+		thistime = read(sock_fd, namebuf + nread,
+				talloc_get_size(namebuf) - nread);
+		if (thistime <= 0) {
+			return false;
+		}
+
+		nread += thistime;
+
+		if (nread == talloc_get_size(namebuf)) {
+			namebuf = talloc_realloc(
+				NULL, namebuf, char,
+				talloc_get_size(namebuf) * 2);
+			if (namebuf == NULL) {
+				return false;
+			}
+			*pnamebuf = namebuf;
+		}
+	} while (namebuf[nread - 1] != '\0');
+
+	fd = open(namebuf, O_RDONLY);
+	if (fd == -1) {
+		goto done;
+	}
+	nread = read(fd, filebuf, to_read);
+	close(fd);
+
+ done:
+	sys_write_v(sock_fd, &c, 1);
+	return true;
+}
+
+static bool preopen_helper(int fd, size_t to_read)
+{
+	char *namebuf;
+	void *readbuf;
+
+	namebuf = talloc_array(NULL, char, 1024);
+	if (namebuf == NULL) {
+		return false;
+	}
+
+	readbuf = talloc_size(NULL, to_read);
+	if (readbuf == NULL) {
+		TALLOC_FREE(namebuf);
+		return false;
+	}
+
+	while (preopen_helper_open_one(fd, &namebuf, to_read, readbuf)) {
+		;
+	}
+
+	TALLOC_FREE(readbuf);
+	TALLOC_FREE(namebuf);
+	return false;
+}
+
+static NTSTATUS preopen_init_helper(struct preopen_helper *h)
+{
+	int fdpair[2];
+	NTSTATUS status;
+
+	if (socketpair(AF_UNIX, SOCK_STREAM, 0, fdpair) == -1) {
+		status = map_nt_error_from_unix(errno);
+		DEBUG(10, ("socketpair() failed: %s\n", strerror(errno)));
+		return status;
+	}
+
+	h->pid = fork();
+
+	if (h->pid == -1) {
+		return map_nt_error_from_unix(errno);
+	}
+
+	if (h->pid == 0) {
+		close(fdpair[0]);
+		preopen_helper(fdpair[1], h->state->to_read);
+		exit(0);
+	}
+	close(fdpair[1]);
+	h->fd = fdpair[0];
+	h->fde = tevent_add_fd(global_event_context(), h->state, h->fd,
+			      TEVENT_FD_READ, preopen_helper_readable, h);
+	if (h->fde == NULL) {
+		close(h->fd);
+		h->fd = -1;
+		return NT_STATUS_NO_MEMORY;
+	}
+	h->busy = false;
+	return NT_STATUS_OK;
+}
+
+static NTSTATUS preopen_init_helpers(TALLOC_CTX *mem_ctx, size_t to_read,
+				     int num_helpers, int queue_max,
+				     struct preopen_state **presult)
+{
+	struct preopen_state *result;
+	int i;
+
+	result = talloc(mem_ctx, struct preopen_state);
+	if (result == NULL) {
+		return NT_STATUS_NO_MEMORY;
+	}
+
+	result->num_helpers = num_helpers;
+	result->helpers = talloc_array(result, struct preopen_helper,
+				       num_helpers);
+	if (result->helpers == NULL) {
+		TALLOC_FREE(result);
+		return NT_STATUS_NO_MEMORY;
+	}
+
+	result->to_read = to_read;
+	result->queue_max = queue_max;
+	result->template_fname = NULL;
+	result->fnum_sent = 0;
+	result->fnum_queue_end = 0;
+
+	for (i=0; i<num_helpers; i++) {
+		result->helpers[i].state = result;
+		result->helpers[i].fd = -1;
+	}
+
+	talloc_set_destructor(result, preopen_helpers_destructor);
+
+	for (i=0; i<num_helpers; i++) {
+		preopen_init_helper(&result->helpers[i]);
+	}
+
+	*presult = result;
+	return NT_STATUS_OK;
+}
+
+static void preopen_free_helpers(void **ptr)
+{
+	TALLOC_FREE(*ptr);
+}
+
+static struct preopen_state *preopen_state_get(vfs_handle_struct *handle)
+{
+	struct preopen_state *state;
+	NTSTATUS status;
+	const char *namelist;
+
+	if (SMB_VFS_HANDLE_TEST_DATA(handle)) {
+		SMB_VFS_HANDLE_GET_DATA(handle, state, struct preopen_state,
+					return NULL);
+		return state;
+	}
+
+	namelist = lp_parm_const_string(SNUM(handle->conn), "preopen", "names",
+					NULL);
+
+	if (namelist == NULL) {
+		return NULL;
+	}
+
+	status = preopen_init_helpers(
+		NULL,
+		lp_parm_int(SNUM(handle->conn), "preopen", "num_bytes", 1),
+		lp_parm_int(SNUM(handle->conn), "preopen", "helpers", 1),
+		lp_parm_int(SNUM(handle->conn), "preopen", "queuelen", 10),
+		&state);
+	if (!NT_STATUS_IS_OK(status)) {
+		return NULL;
+	}
+
+	state->queue_dbglvl = lp_parm_int(SNUM(handle->conn), "preopen", "queue_log_level", DBGLVL_DEBUG);
+	state->nomatch_dbglvl = lp_parm_int(SNUM(handle->conn), "preopen", "nomatch_log_level", DBGLVL_INFO);
+	state->match_dbglvl = lp_parm_int(SNUM(handle->conn), "preopen", "match_log_level", DBGLVL_INFO);
+	state->reset_dbglvl = lp_parm_int(SNUM(handle->conn), "preopen", "reset_log_level", DBGLVL_INFO);
+	state->nodigits_dbglvl = lp_parm_int(SNUM(handle->conn), "preopen", "nodigits_log_level", DBGLVL_WARNING);
+	state->founddigits_dbglvl = lp_parm_int(SNUM(handle->conn), "preopen", "founddigits_log_level", DBGLVL_NOTICE);
+	state->push_dbglvl = lp_parm_int(SNUM(handle->conn), "preopen", "push_log_level", DBGLVL_NOTICE);
+
+	if (lp_parm_bool(SNUM(handle->conn), "preopen", "posix-basic-regex", false)) {
+		status = samba_path_matching_regex_sub1_create(state,
+							       namelist,
+							       &state->preopen_names);
+	} else {
+		status = samba_path_matching_mswild_create(state,
+							   true, /* case_sensitive */
+							   namelist,
+							   &state->preopen_names);
+	}
+	if (!NT_STATUS_IS_OK(status)) {
+		TALLOC_FREE(state);
+		return NULL;
+	}
+	state->last_match_idx = -1;
+
+	if (!SMB_VFS_HANDLE_TEST_DATA(handle)) {
+		SMB_VFS_HANDLE_SET_DATA(handle, state, preopen_free_helpers,
+					struct preopen_state, return NULL);
+	}
+
+	return state;
+}
+
+static bool preopen_parse_fname(const char *fname, uint64_t *pnum,
+				size_t *pstart_idx, int *pnum_digits)
+{
+	char digits[PREOPEN_MAX_DIGITS+1] = { 0, };
+	const char *p;
+	char *q = NULL;
+	unsigned long long num;
+	size_t start_idx = 0;
+	int num_digits = -1;
+	int error = 0;
+
+	if (*pstart_idx > 0 && *pnum_digits > 0) {
+		/*
+		 * If the caller knowns
+		 * how many digits are expected
+		 * and on what position,
+		 * we should copy the exact
+		 * subset before we start
+		 * parsing the string into a number
+		 */
+
+		if (*pnum_digits > PREOPEN_MAX_DIGITS) {
+			/*
+			 * a string with as much digits as
+			 * PREOPEN_MAX_DIGITS is the longest
+			 * string that would make any sense for us.
+			 *
+			 * The rest will be checked via
+			 * smb_strtoull().
+			 */
+			return false;
+		}
+		p = fname + *pstart_idx;
+		memcpy(digits, p, *pnum_digits);
+		p = digits;
+		start_idx = *pstart_idx;
+		goto parse;
+	}
+
+	p = strrchr_m(fname, '/');
+	if (p == NULL) {
+		p = fname;
+	}
+
+	p += 1;
+	while (p[0] != '\0') {
+		if (isdigit(p[0]) && isdigit(p[1]) && isdigit(p[2])) {
+			break;
+		}
+		p += 1;
+	}
+	if (*p == '\0') {
+		/* no digits around */
+		return false;
+	}
+
+	start_idx = (p - fname);
+
+parse:
+	num = smb_strtoull(p, (char **)&q, 10, &error, SMB_STR_STANDARD);
+	if (error != 0) {
+		return false;
+	}
+
+	if (num >= PREOPEN_MAX_NUMBER) {
+		/* overflow */
+		return false;
+	}
+
+	num_digits = (q - p);
+
+	if (*pnum_digits != -1 && *pnum_digits != num_digits) {
+		/*
+		 * If the caller knowns how many digits
+		 * it expects we should fail if we got something
+		 * different.
+		 */
+		return false;
+	}
+
+	*pnum = num;
+	*pstart_idx = start_idx;
+	*pnum_digits = num_digits;
+	return true;
+}
+
+static uint64_t num_digits_max_value(int num_digits)
+{
+	uint64_t num_max = 1;
+	int i;
+
+	if (num_digits < 1) {
+		return 0;
+	}
+	if (num_digits >= PREOPEN_MAX_DIGITS) {
+		return PREOPEN_MAX_NUMBER;
+	}
+
+	for (i = 0; i < num_digits; i++) {
+		num_max *= 10;
+	}
+
+	/*
+	 * We actually want
+	 * 9   instead of 10
+	 * 99  instead of 100
+	 * 999 instead of 1000
+	 */
+	return num_max - 1;
+}
+
+static int preopen_openat(struct vfs_handle_struct *handle,
+			  const struct files_struct *dirfsp,
+			  const struct smb_filename *smb_fname,
+			  struct files_struct *fsp,
+			  const struct vfs_open_how *how)
+{
+	const char *dirname = dirfsp->fsp_name->base_name;
+	struct preopen_state *state;
+	int res;
+	uint64_t num;
+	uint64_t num_max;
+	NTSTATUS status;
+	char *new_template = NULL;
+	size_t new_start = 0;
+	int new_digits = -1;
+	size_t new_end = 0;
+	ssize_t match_idx = -1;
+	ssize_t replace_start = -1;
+	ssize_t replace_end = -1;
+	bool need_reset = false;
+
+	DBG_DEBUG("called on %s\n", smb_fname_str_dbg(smb_fname));
+
+	state = preopen_state_get(handle);
+	if (state == NULL) {
+		return SMB_VFS_NEXT_OPENAT(handle,
+					   dirfsp,
+					   smb_fname,
+					   fsp,
+					   how);
+	}
+
+	res = SMB_VFS_NEXT_OPENAT(handle, dirfsp, smb_fname, fsp, how);
+	if (res == -1) {
+		return -1;
+	}
+
+	if ((how->flags & O_ACCMODE) != O_RDONLY) {
+		return res;
+	}
+
+	/*
+	 * Make sure we can later construct an absolute pathname
+	 */
+	if (dirname[0] != '/') {
+		return res;
+	}
+	/*
+	 * There's no point in preopen the directory itself.
+	 */
+	if (ISDOT(smb_fname->base_name)) {
+		return res;
+	}
+	/*
+	 * If we got an absolute path in
+	 * smb_fname it's most likely the
+	 * reopen via /proc/self/fd/$fd
+	 */
+	if (smb_fname->base_name[0] == '/') {
+		return res;
+	}
+
+	status = samba_path_matching_check_last_component(state->preopen_names,
+							  smb_fname->base_name,
+							  &match_idx,
+							  &replace_start,
+							  &replace_end);
+	if (!NT_STATUS_IS_OK(status)) {
+		match_idx = -1;
+	}
+	if (match_idx < 0) {
+		DBG_PREFIX(state->nomatch_dbglvl, (
+			   "No match with the preopen:names list by name[%s]\n",
+		           smb_fname_str_dbg(smb_fname)));
+		return res;
+	}
+
+	if (replace_start != -1 && replace_end != -1) {
+		DBG_PREFIX(state->match_dbglvl, (
+			   "Pattern(idx=%zd) from preopen:names list matched name[%s] hints(start=%zd,end=%zd)\n",
+			   match_idx, smb_fname_str_dbg(smb_fname), replace_start, replace_end));
+	} else {
+		DBG_PREFIX(state->match_dbglvl, (
+			   "Pattern(idx=%zd) from preopen:names list matched name[%s]\n",
+			   match_idx, smb_fname_str_dbg(smb_fname)));
+	}
+
+	new_template = talloc_asprintf(
+		state, "%s/%s",
+		dirname, smb_fname->base_name);
+	if (new_template == NULL) {
+		DBG_ERR("talloc_asprintf(%s/%s) failed\n",
+			dirname, smb_fname_str_dbg(smb_fname));
+		return res;
+	}
+
+	if (replace_start != -1 && replace_end != -1) {
+		size_t dirofs = strlen(dirname) + 1;
+		new_start = dirofs + replace_start;
+		new_digits = replace_end - replace_start;
+	}
+
+	if (!preopen_parse_fname(new_template, &num,
+				 &new_start, &new_digits)) {
+		DBG_PREFIX(state->nodigits_dbglvl, (
+			   "Pattern(idx=%zd) no valid digits found on fullpath[%s]\n",
+			   match_idx, new_template));
+		TALLOC_FREE(new_template);
+		return res;
+	}
+	new_end = new_start + new_digits;
+
+	DBG_PREFIX(state->founddigits_dbglvl, (
+		   "Pattern(idx=%zd) found num_digits[%d] start_offset[%zd] parsed_num[%"PRIu64"] fullpath[%s]\n",
+		   match_idx, new_digits, new_start, num, new_template));
+
+	if (state->last_match_idx != match_idx) {
+		/*
+		 * If a different pattern caused the match
+		 * we better reset the queue
+		 */
+		if (state->last_match_idx != -1) {
+			DBG_PREFIX(state->reset_dbglvl, ("RESET: "
+				   "pattern changed from idx=%zd to idx=%zd by fullpath[%s]\n",
+				   state->last_match_idx, match_idx, new_template));
+		}
+		need_reset = true;
+	} else if (state->number_start != new_start) {
+		/*
+		 * If the digits started at a different position
+		 * we better reset the queue
+		 */
+		DBG_PREFIX(state->reset_dbglvl, ("RESET: "
+			   "start_offset changed from byte=%zd to byte=%zd by fullpath[%s]\n",
+			   state->number_start, new_start, new_template));
+		need_reset = true;
+	} else if (state->num_digits != new_digits) {
+		/*
+		 * If number of digits changed
+		 * we better reset the queue
+		 */
+		DBG_PREFIX(state->reset_dbglvl, ("RESET: "
+			   "num_digits changed %d to %d by fullpath[%s]\n",
+			   state->num_digits, new_digits, new_template));
+		need_reset = true;
+	} else if (strncmp(state->template_fname, new_template, new_start) != 0) {
+		/*
+		 * If name before the digits changed
+		 * we better reset the queue
+		 */
+		DBG_PREFIX(state->reset_dbglvl, ("RESET: "
+			   "leading pathprefix[%.*s] changed by fullpath[%s]\n",
+			   (int)state->number_start, state->template_fname, new_template));
+		need_reset = true;
+	} else if (strcmp(state->template_fname + new_end, new_template + new_end) != 0) {
+		/*
+		 * If name after the digits changed
+		 * we better reset the queue
+		 */
+		DBG_PREFIX(state->reset_dbglvl, ("RESET: "
+			   "trailing suffix[%s] changed by fullpath[%s]\n",
+			   state->template_fname + new_end, new_template));
+		need_reset = true;
+	}
+
+	if (need_reset) {
+		/*
+		 * Reset the queue
+		 */
+		state->fnum_sent = 0;
+		state->fnum_queue_end = 0;
+		state->last_match_idx = match_idx;
+	}
+
+	TALLOC_FREE(state->template_fname);
+	state->template_fname = new_template;
+	state->number_start = new_start;
+	state->num_digits = new_digits;
+
+	if (num > state->fnum_sent) {
+		/*
+		 * Helpers were too slow, there's no point in reading
+		 * files in helpers that we already read in the
+		 * parent.
+		 */
+		state->fnum_sent = num;
+	}
+
+	if ((state->fnum_queue_end != 0) /* Something was started earlier */
+	    && (num < (state->fnum_queue_end - state->queue_max))) {
+		/*
+		 * "num" is before the queue we announced. This means
+		 * a new run is started.
+		 */
+		state->fnum_sent = num;
+	}
+
+	num_max = num_digits_max_value(state->num_digits);
+	state->fnum_queue_end = MIN(num_max, num + state->queue_max);
+
+	DBG_PREFIX(state->queue_dbglvl, ("BEFORE: preopen_queue_run\n"));
+	preopen_queue_run(state);
+	DBG_PREFIX(state->queue_dbglvl, ("AFTER: preopen_queue_run\n"));
+
+	return res;
+}
+
+static struct vfs_fn_pointers vfs_preopen_fns = {
+	.openat_fn = preopen_openat,
+};
+
+static_decl_vfs;
+NTSTATUS vfs_preopen_init(TALLOC_CTX *ctx)
+{
+	NTSTATUS status;
+
+	status = smb_register_vfs(SMB_VFS_INTERFACE_VERSION,
+				  "preopen",
+				  &vfs_preopen_fns);
+	if (!NT_STATUS_IS_OK(status)) {
+		return status;
+	}
+
+	vfs_preopen_debug_level = debug_add_class("preopen");
+	if (vfs_preopen_debug_level == -1) {
+		vfs_preopen_debug_level = DBGC_VFS;
+		DBG_ERR("Couldn't register custom debugging class!\n");
+	} else {
+		DBG_DEBUG("Debug class number of 'preopen': %d\n",
+			  vfs_preopen_debug_level);
+	}
+
+	return NT_STATUS_OK;
+}