Add a vfs_preopen module to hide fs latencies

docs-xml/manpages-3/vfs_preopen.8.xml

@@ -0,0 +1,115 @@
+<?xml version="1.0" encoding="iso-8859-1"?>
+<!DOCTYPE refentry PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
+<refentry id="vfs_preopen.8">
+
+<refmeta>
+	<refentrytitle>vfs_preopen</refentrytitle>
+	<manvolnum>8</manvolnum>
+	<refmiscinfo class="source">Samba</refmiscinfo>
+	<refmiscinfo class="manual">System Administration tools</refmiscinfo>
+	<refmiscinfo class="version">3.3</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+	<refname>vfs_preopen</refname>
+	<refpurpose>Hide read latencies for applications reading numbered files</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+	<cmdsynopsis>
+		<command>vfs objects = preopen</command>
+	</cmdsynopsis>
+</refsynopsisdiv>
+
+<refsect1>
+	<title>DESCRIPTION</title>
+
+	<para>This VFS module is part of the
+	<citerefentry><refentrytitle>samba</refentrytitle>
+	<manvolnum>7</manvolnum></citerefentry> suite.</para>
+
+	<para>This module assists applications that want to read numbered
+	files in sequence with very strict latency requirements. One area
+	where this happens in video streaming applications that want to read
+	one file per frame.</para>
+
+	<para>When you use this module, a number of helper processes is
+	started that speculatively open files and read a number of bytes to
+	prime the file system cache, so that later on when the real
+	application's request comes along, no disk access is necessary.</para>
+
+	<para>This module is stackable.</para>
+
+</refsect1>
+
+
+<refsect1>
+	<title>OPTIONS</title>
+
+	<variablelist>
+
+		<varlistentry>
+		<term>preopen:names = /pattern/</term>
+		<listitem>
+		<para>
+		preopen:names specifies the file name pattern which should
+		trigger the preopen helpers to do their work. We assume that
+		the files are numbered incrementally. So if your file names
+		are numbered FRAME00000.frm FRAME00001.frm and so on you would
+		list them as <command>preopen:names=/FRAME*.frm/</command>
+		</para>
+		</listitem>
+		</varlistentry>
+
+		<varlistentry>
+		<term>preopen:num_bytes = BYTES</term>
+		<listitem>
+		<para>
+		Specifies the number of bytes the helpers should speculatively
+		read, defaults to 1.
+		</para>
+		</listitem>
+		</varlistentry>
+
+		<varlistentry>
+		<term>preopen:helpers = NUM-PROCS</term>
+		<listitem>
+		<para>
+		Number of forked helper processes, defaults to 1.
+		</para>
+		</listitem>
+		</varlistentry>
+
+		<varlistentry>
+		<term>preopen:queuelen = NUM-FILES</term>
+		<listitem>
+		<para>
+		Number of files that should be speculatively opened. Defaults
+		to the 10 subsequent files.
+		</para>
+		</listitem>
+		</varlistentry>
+
+	</variablelist>
+</refsect1>
+
+<refsect1>
+	<title>VERSION</title>
+	<para>This man page is correct for version 3.3 of the Samba suite.
+	</para>
+</refsect1>
+
+<refsect1>
+	<title>AUTHOR</title>
+
+	<para>The original Samba software and related utilities
+	were created by Andrew Tridgell. Samba is now developed
+	by the Samba Team as an Open Source project similar
+	to the way the Linux kernel is developed.</para>
+
+	<para>The PREOPEN VFS module was created with contributions from
+	Volker Lendecke and the developers at IBM.
+	</para>
+</refsect1>
+
+</refentry>

source3/Makefile.in

@@ -667,6 +667,7 @@ VFS_READAHEAD_OBJ = modules/vfs_readahead.o
 VFS_TSMSM_OBJ = modules/vfs_tsmsm.o
 VFS_FILEID_OBJ = modules/vfs_fileid.o
 VFS_AIO_FORK_OBJ = modules/vfs_aio_fork.o
+VFS_PREOPEN_OBJ = modules/vfs_preopen.o
 VFS_SYNCOPS_OBJ = modules/vfs_syncops.o
 VFS_ACL_XATTR_OBJ = modules/vfs_acl_xattr.o
 VFS_ACL_TDB_OBJ = modules/vfs_acl_tdb.o
@@ -2567,6 +2568,10 @@ bin/aio_fork.@SHLIBEXT@: $(BINARY_PREREQS) $(VFS_AIO_FORK_OBJ)
 	@echo "Building plugin $@"
 	@$(SHLD_MODULE) $(VFS_AIO_FORK_OBJ)
 
+bin/preopen.@SHLIBEXT@: $(BINARY_PREREQS) $(VFS_PREOPEN_OBJ)
+	@echo "Building plugin $@"
+	@$(SHLD_MODULE) $(VFS_PREOPEN_OBJ)
+
 bin/acl_xattr.@SHLIBEXT@: $(BINARY_PREREQS) $(VFS_ACL_XATTR_OBJ)
 	@echo "Building plugin $@"
 	@$(SHLD_MODULE) $(VFS_ACL_XATTR_OBJ)

source3/configure.in

@@ -417,7 +417,7 @@ dnl These have to be built static:
 default_static_modules="pdb_smbpasswd pdb_tdbsam pdb_wbc_sam rpc_lsarpc rpc_samr rpc_winreg rpc_initshutdown rpc_dssetup rpc_wkssvc rpc_svcctl rpc_ntsvcs rpc_netlogon rpc_netdfs rpc_srvsvc rpc_spoolss2 rpc_eventlog auth_sam auth_unix auth_winbind auth_wbc auth_server auth_domain auth_builtin auth_netlogond vfs_default nss_info_template"
 
 dnl These are preferably build shared, and static if dlopen() is not available
-default_shared_modules="vfs_recycle vfs_audit vfs_extd_audit vfs_full_audit vfs_netatalk vfs_fake_perms vfs_default_quota vfs_readonly vfs_cap vfs_expand_msdfs vfs_shadow_copy vfs_shadow_copy2 charset_CP850 charset_CP437 auth_script vfs_readahead vfs_xattr_tdb vfs_streams_xattr vfs_streams_depot vfs_acl_xattr vfs_acl_tdb vfs_smb_traffic_analyzer"
+default_shared_modules="vfs_recycle vfs_audit vfs_extd_audit vfs_full_audit vfs_netatalk vfs_fake_perms vfs_default_quota vfs_readonly vfs_cap vfs_expand_msdfs vfs_shadow_copy vfs_shadow_copy2 charset_CP850 charset_CP437 auth_script vfs_readahead vfs_xattr_tdb vfs_streams_xattr vfs_streams_depot vfs_acl_xattr vfs_acl_tdb vfs_smb_traffic_analyzer vfs_preopen"
 
 if test "x$developer" = xyes; then
    default_static_modules="$default_static_modules rpc_rpcecho"
@@ -6185,6 +6185,7 @@ SMB_MODULE(vfs_readahead, \$(VFS_READAHEAD_OBJ), "bin/readahead.$SHLIBEXT", VFS)
 SMB_MODULE(vfs_tsmsm, \$(VFS_TSMSM_OBJ), "bin/tsmsm.$SHLIBEXT", VFS)
 SMB_MODULE(vfs_fileid, \$(VFS_FILEID_OBJ), "bin/fileid.$SHLIBEXT", VFS)
 SMB_MODULE(vfs_aio_fork, \$(VFS_AIO_FORK_OBJ), "bin/aio_fork.$SHLIBEXT", VFS)
+SMB_MODULE(vfs_preopen, \$(VFS_PREOPEN_OBJ), "bin/preopen.$SHLIBEXT", VFS)
 SMB_MODULE(vfs_syncops, \$(VFS_SYNCOPS_OBJ), "bin/syncops.$SHLIBEXT", VFS)
 SMB_MODULE(vfs_zfsacl, \$(VFS_ZFSACL_OBJ), "bin/zfsacl.$SHLIBEXT", VFS)
 SMB_MODULE(vfs_notify_fam, \$(VFS_NOTIFY_FAM_OBJ), "bin/notify_fam.$SHLIBEXT", VFS)

source3/modules/vfs_preopen.c

@@ -0,0 +1,456 @@
+/*
+ * 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"
+
+struct preopen_state;
+
+struct preopen_helper {
+	struct preopen_state *state;
+	struct fd_event *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;
+
+	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? */
+
+	int fnum_sent;		/* last fname sent to children */
+
+	int fnum_queue_end;	/* last fname to be sent, based on
+				 * last open call + preopen:queuelen
+				 */
+
+	name_compare_entry *preopen_names;
+};
+
+static void preopen_helper_destroy(struct preopen_helper *c)
+{
+	int status;
+	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;
+
+	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 */
+			return;
+		}
+
+		snprintf(state->template_fname + state->number_start,
+			 state->num_digits + 1,
+			 "%.*lu", state->num_digits,
+			 (long unsigned int)(state->fnum_sent + 1));
+		*pdelimiter = delimiter;
+
+		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;
+	}
+}
+
+static void preopen_helper_readable(struct event_context *ev,
+				    struct fd_event *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 & EVENT_FD_READ) == 0) {
+		return;
+	}
+
+	nread = read(helper->fd, &c, 1);
+	if (nread <= 0) {
+		preopen_helper_destroy(helper);
+		return;
+	}
+
+	helper->busy = false;
+
+	preopen_queue_run(state);
+}
+
+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 nwritten, nread;
+	char c = 0;
+	int fd;
+
+	nread = 0;
+
+	while ((nread == 0) || (namebuf[nread-1] != '\0')) {
+		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_ARRAY(
+				NULL, namebuf, char,
+				talloc_get_size(namebuf) * 2);
+			if (namebuf == NULL) {
+				return false;
+			}
+			*pnamebuf = namebuf;
+		}
+	}
+
+	fd = open(namebuf, O_RDONLY);
+	if (fd == -1) {
+		goto done;
+	}
+	nread = read(fd, filebuf, to_read);
+	close(fd);
+
+ done:
+	nwritten = write(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 = sys_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 = event_add_fd(smbd_event_context(), h->state, h->fd,
+			      EVENT_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;
+
+	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;
+	}
+
+	set_namearray(&state->preopen_names, (char *)namelist);
+
+	if (state->preopen_names == NULL) {
+		TALLOC_FREE(state);
+		return NULL;
+	}
+
+	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, unsigned long *pnum,
+				size_t *pstart_idx, int *pnum_digits)
+{
+	const char *p, *q;
+	unsigned long num;
+
+	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;
+	}
+
+	num = strtoul(p, (char **)&q, 10);
+
+	if (num+1 < num) {
+		/* overflow */
+		return false;
+	}
+
+	*pnum = num;
+	*pstart_idx = (p - fname);
+	*pnum_digits = (q - p);
+	return true;
+}
+
+static int preopen_open(vfs_handle_struct *handle, const char *fname,
+			files_struct *fsp, int flags, mode_t mode)
+{
+	struct preopen_state *state;
+	int res;
+	unsigned long num;
+
+	DEBUG(10, ("preopen_open called on %s\n", fname));
+
+	state = preopen_state_get(handle);
+	if (state == NULL) {
+		return SMB_VFS_NEXT_OPEN(handle, fname, fsp, flags, mode);
+	}
+
+	res = SMB_VFS_NEXT_OPEN(handle, fname, fsp, flags, mode);
+	if (res == -1) {
+		return -1;
+	}
+
+	if (flags != O_RDONLY) {
+		return res;
+	}
+
+	if (!is_in_path(fname, state->preopen_names, true)) {
+		DEBUG(10, ("%s does not match the preopen:names list\n",
+			   fname));
+		return res;
+	}
+
+	TALLOC_FREE(state->template_fname);
+	state->template_fname = talloc_asprintf(
+		state, "%s/%s", fsp->conn->connectpath, fname);
+
+	if (state->template_fname == NULL) {
+		return res;
+	}
+
+	if (!preopen_parse_fname(state->template_fname, &num,
+				 &state->number_start, &state->num_digits)) {
+		TALLOC_FREE(state->template_fname);
+		return res;
+	}
+
+	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;
+	}
+
+	state->fnum_queue_end = num + state->queue_max;
+
+	preopen_queue_run(state);
+
+	return res;
+}
+
+/* VFS operations structure */
+
+static vfs_op_tuple preopen_ops[] = {
+	{SMB_VFS_OP(preopen_open),	SMB_VFS_OP_OPEN,
+	 SMB_VFS_LAYER_TRANSPARENT},
+	{SMB_VFS_OP(NULL),		SMB_VFS_OP_NOOP,
+	 SMB_VFS_LAYER_NOOP}
+};
+
+NTSTATUS vfs_preopen_init(void);
+NTSTATUS vfs_preopen_init(void)
+{
+	return smb_register_vfs(SMB_VFS_INTERFACE_VERSION,
+				"preopen", preopen_ops);
+}