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* [PATCH 1/3] cifs: Add support for root file systems
@ 2019-07-16 22:04 Paulo Alcantara (SUSE)
  2019-07-16 22:04 ` [PATCH 2/3] init: Support mounting root file systems over SMB Paulo Alcantara (SUSE)
  2019-07-16 22:04 ` [PATCH 3/3] ipconfig: Handle CONFIG_CIFS_ROOT option Paulo Alcantara (SUSE)
  0 siblings, 2 replies; 3+ messages in thread
From: Paulo Alcantara (SUSE) @ 2019-07-16 22:04 UTC (permalink / raw)
  To: linux-kernel, netdev, linux-cifs, samba-technical
  Cc: Paulo Alcantara (SUSE), Steve French

Introduce a new CONFIG_CIFS_ROOT option to handle root file systems
over a SMB share.

In order to mount the root file system during the init process, make
cifs.ko perform non-blocking socket operations while mounting and
accessing it.

Cc: Steve French <smfrench@gmail.com>
Signed-off-by: Paulo Alcantara (SUSE) <paulo@paulo.ac>
---
 Documentation/filesystems/cifs/cifsroot.txt | 97 +++++++++++++++++++++
 fs/cifs/Kconfig                             |  8 ++
 fs/cifs/Makefile                            |  2 +
 fs/cifs/cifsglob.h                          |  2 +
 fs/cifs/cifsroot.c                          | 83 ++++++++++++++++++
 fs/cifs/connect.c                           | 17 +++-
 include/linux/root_dev.h                    |  1 +
 7 files changed, 207 insertions(+), 3 deletions(-)
 create mode 100644 Documentation/filesystems/cifs/cifsroot.txt
 create mode 100644 fs/cifs/cifsroot.c

diff --git a/Documentation/filesystems/cifs/cifsroot.txt b/Documentation/filesystems/cifs/cifsroot.txt
new file mode 100644
index 000000000000..0fa1a2c36a40
--- /dev/null
+++ b/Documentation/filesystems/cifs/cifsroot.txt
@@ -0,0 +1,97 @@
+Mounting root file system via SMB (cifs.ko)
+===========================================
+
+Written 2019 by Paulo Alcantara <palcantara@suse.de>
+Written 2019 by Aurelien Aptel <aaptel@suse.com>
+
+The CONFIG_CIFS_ROOT option enables experimental root file system
+support over the SMB protocol via cifs.ko.
+
+It introduces a new kernel command-line option called 'cifsroot='
+which will tell the kernel to mount the root file system over the
+network by utilizing SMB or CIFS protocol.
+
+In order to mount, the network stack will also need to be set up by
+using 'ip=' config option. For more details, see
+Documentation/filesystems/nfs/nfsroot.txt.
+
+A CIFS root mount currently requires the use of SMB1+UNIX Extensions
+which is only supported by the Samba server. SMB1 is the older
+deprecated version of the protocol but it has been extended to support
+POSIX features (See [1]). The equivalent extensions for the newer
+recommended version of the protocol (SMB3) have not been fully
+implemented yet which means SMB3 doesn't support some required POSIX
+file system objects (e.g. block devices, pipes, sockets).
+
+As a result, a CIFS root will default to SMB1 for now but the version
+to use can nonetheless be changed via the 'vers=' mount option.  This
+default will change once the SMB3 POSIX extensions are fully
+implemented.
+
+Server configuration
+====================
+
+To enable SMB1+UNIX extensions you will need to set these global
+settings in Samba smb.conf:
+
+    [global]
+    server min protocol = NT1
+    unix extension = yes        # default
+
+Kernel command line
+===================
+
+root=/dev/cifs
+
+This is just a virtual device that basically tells the kernel to mount
+the root file system via SMB protocol.
+
+cifsroot=//<server-ip>/<share>[,options]
+
+Enables the kernel to mount the root file system via SMB that are
+located in the <server-ip> and <share> specified in this option.
+
+The default mount options are set in fs/cifs/cifsroot.c.
+
+server-ip
+	IPv4 address of the server.
+
+share
+	Path to SMB share (rootfs).
+
+options
+	Optional mount options. For more information, see mount.cifs(8).
+
+Examples
+========
+
+Export root file system as a Samba share in smb.conf file.
+
+...
+[linux]
+	path = /path/to/rootfs
+	read only = no
+	guest ok = yes
+	force user = root
+	force group = root
+	browseable = yes
+	writeable = yes
+	admin users = root
+	public = yes
+	create mask = 0777
+	directory mask = 0777
+...
+
+Restart smb service.
+
+# systemctl restart smb
+
+Test it under QEMU on a kernel built with CONFIG_CIFS_ROOT and
+CONFIG_IP_PNP options enabled.
+
+# qemu-system-x86_64 -enable-kvm -cpu host -m 1024 \
+  -kernel /path/to/linux/arch/x86/boot/bzImage -nographic \
+  -append "root=/dev/cifs rw ip=dhcp cifsroot=//10.0.2.2/linux,username=foo,password=bar console=ttyS0 3"
+
+
+1: https://wiki.samba.org/index.php/UNIX_Extensions
diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index 523e9ea78a28..d28d62532318 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -217,3 +217,11 @@ config CIFS_FSCACHE
 	  Makes CIFS FS-Cache capable. Say Y here if you want your CIFS data
 	  to be cached locally on disk through the general filesystem cache
 	  manager. If unsure, say N.
+
+config CIFS_ROOT
+	bool "SMB root file system (Experimental)"
+	depends on CIFS=y && IP_PNP
+	help
+	  Enables root file system support over SMB protocol.
+
+	  Most people say N here.
diff --git a/fs/cifs/Makefile b/fs/cifs/Makefile
index 51af69a1a328..45cf67f37487 100644
--- a/fs/cifs/Makefile
+++ b/fs/cifs/Makefile
@@ -22,3 +22,5 @@ cifs-$(CONFIG_CIFS_DFS_UPCALL) += dns_resolve.o cifs_dfs_ref.o dfs_cache.o
 cifs-$(CONFIG_CIFS_FSCACHE) += fscache.o cache.o
 
 cifs-$(CONFIG_CIFS_SMB_DIRECT) += smbdirect.o
+
+cifs-$(CONFIG_CIFS_ROOT) += cifsroot.o
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 4777b3c4a92c..ac7e433a5b94 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -600,6 +600,7 @@ struct smb_vol {
 	__u64 snapshot_time; /* needed for timewarp tokens */
 	__u32 handle_timeout; /* persistent and durable handle timeout in ms */
 	unsigned int max_credits; /* smb3 max_credits 10 < credits < 60000 */
+	bool rootfs:1; /* if it's a SMB root file system */
 };
 
 /**
@@ -752,6 +753,7 @@ struct TCP_Server_Info {
 	 * reconnect.
 	 */
 	int nr_targets;
+	bool noblockcnt; /* use non-blocking connect() */
 };
 
 struct cifs_credits {
diff --git a/fs/cifs/cifsroot.c b/fs/cifs/cifsroot.c
new file mode 100644
index 000000000000..8760d9cbf25e
--- /dev/null
+++ b/fs/cifs/cifsroot.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SMB root file system support
+ *
+ * Copyright (c) 2019 Paulo Alcantara <palcantara@suse.de>
+ */
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/types.h>
+#include <linux/ctype.h>
+#include <linux/string.h>
+#include <linux/root_dev.h>
+#include <linux/kernel.h>
+#include <linux/in.h>
+#include <linux/inet.h>
+#include <net/ipconfig.h>
+
+#define DEFAULT_MNT_OPTS \
+	"vers=1.0,cifsacl,mfsymlinks,rsize=1048576,wsize=65536,uid=0,gid=0," \
+	"hard,rootfs"
+
+static char root_dev[2048] __initdata = "";
+static char root_opts[1024] __initdata = DEFAULT_MNT_OPTS;
+
+static __be32 __init parse_srvaddr(char *start, char *end)
+{
+	char addr[sizeof("aaa.bbb.ccc.ddd")];
+	int i = 0;
+
+	while (start < end && i < sizeof(addr) - 1) {
+		if (isdigit(*start) || *start == '.')
+			addr[i++] = *start;
+		start++;
+	}
+	addr[i] = '\0';
+	return in_aton(addr);
+}
+
+/* cifsroot=//<server-ip>/<share>[,options] */
+static int __init cifs_root_setup(char *line)
+{
+	char *s;
+	int len;
+	__be32 srvaddr = htonl(INADDR_NONE);
+
+	ROOT_DEV = Root_CIFS;
+
+	if (strlen(line) > 3 && line[0] == '/' && line[1] == '/') {
+		s = strchr(&line[2], '/');
+		if (!s || s[1] == '\0')
+			return 1;
+
+		s = strchrnul(s, ',');
+		len = s - line + 1;
+		if (len <= sizeof(root_dev)) {
+			strlcpy(root_dev, line, len);
+			srvaddr = parse_srvaddr(&line[2], s);
+			if (*s) {
+				snprintf(root_opts, sizeof(root_opts), "%s,%s",
+					 DEFAULT_MNT_OPTS, s + 1);
+			}
+		}
+	}
+
+	root_server_addr = srvaddr;
+
+	return 1;
+}
+
+__setup("cifsroot=", cifs_root_setup);
+
+int __init cifs_root_data(char **dev, char **opts)
+{
+	if (!root_dev[0] || root_server_addr == htonl(INADDR_NONE)) {
+		printk(KERN_ERR "Root-CIFS: no SMB server address\n");
+		return -1;
+	}
+
+	*dev = root_dev;
+	*opts = root_opts;
+
+	return 0;
+}
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 714a359c7c8d..ca6b04af727f 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -96,7 +96,7 @@ enum {
 	Opt_multiuser, Opt_sloppy, Opt_nosharesock,
 	Opt_persistent, Opt_nopersistent,
 	Opt_resilient, Opt_noresilient,
-	Opt_domainauto, Opt_rdma,
+	Opt_domainauto, Opt_rdma, Opt_rootfs,
 
 	/* Mount options which take numeric value */
 	Opt_backupuid, Opt_backupgid, Opt_uid,
@@ -259,6 +259,7 @@ static const match_table_t cifs_mount_option_tokens = {
 	{ Opt_ignore, "nomand" },
 	{ Opt_ignore, "relatime" },
 	{ Opt_ignore, "_netdev" },
+	{ Opt_rootfs, "rootfs" },
 
 	{ Opt_err, NULL }
 };
@@ -1744,6 +1745,11 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 		case Opt_nodfs:
 			vol->nodfs = 1;
 			break;
+		case Opt_rootfs:
+#ifdef CONFIG_CIFS_ROOT
+			vol->rootfs = true;
+#endif
+			break;
 		case Opt_posixpaths:
 			vol->posix_paths = 1;
 			break;
@@ -2662,7 +2668,8 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 		goto out_err_crypto_release;
 	}
 
-	tcp_ses->noblocksnd = volume_info->noblocksnd;
+	tcp_ses->noblockcnt = volume_info->rootfs;
+	tcp_ses->noblocksnd = volume_info->noblocksnd || volume_info->rootfs;
 	tcp_ses->noautotune = volume_info->noautotune;
 	tcp_ses->tcp_nodelay = volume_info->sockopt_tcp_nodelay;
 	tcp_ses->rdma = volume_info->rdma;
@@ -3768,7 +3775,11 @@ generic_ip_connect(struct TCP_Server_Info *server)
 		 socket->sk->sk_sndbuf,
 		 socket->sk->sk_rcvbuf, socket->sk->sk_rcvtimeo);
 
-	rc = socket->ops->connect(socket, saddr, slen, 0);
+	rc = socket->ops->connect(socket, saddr, slen,
+				  server->noblockcnt ? O_NONBLOCK : 0);
+
+	if (rc == -EINPROGRESS)
+		rc = 0;
 	if (rc < 0) {
 		cifs_dbg(FYI, "Error %d connecting to server\n", rc);
 		sock_release(socket);
diff --git a/include/linux/root_dev.h b/include/linux/root_dev.h
index bab671b0782f..4e78651371ba 100644
--- a/include/linux/root_dev.h
+++ b/include/linux/root_dev.h
@@ -8,6 +8,7 @@
 
 enum {
 	Root_NFS = MKDEV(UNNAMED_MAJOR, 255),
+	Root_CIFS = MKDEV(UNNAMED_MAJOR, 254),
 	Root_RAM0 = MKDEV(RAMDISK_MAJOR, 0),
 	Root_RAM1 = MKDEV(RAMDISK_MAJOR, 1),
 	Root_FD0 = MKDEV(FLOPPY_MAJOR, 0),
-- 
2.22.0


^ permalink raw reply	[flat|nested] 3+ messages in thread

* [PATCH 2/3] init: Support mounting root file systems over SMB
  2019-07-16 22:04 [PATCH 1/3] cifs: Add support for root file systems Paulo Alcantara (SUSE)
@ 2019-07-16 22:04 ` Paulo Alcantara (SUSE)
  2019-07-16 22:04 ` [PATCH 3/3] ipconfig: Handle CONFIG_CIFS_ROOT option Paulo Alcantara (SUSE)
  1 sibling, 0 replies; 3+ messages in thread
From: Paulo Alcantara (SUSE) @ 2019-07-16 22:04 UTC (permalink / raw)
  To: linux-kernel, netdev, linux-cifs, samba-technical
  Cc: Paulo Alcantara (SUSE), Andrew Morton

Add a new virtual device named /dev/cifs (0xfe) to tell the kernel to
mount the root file system over the network by using SMB protocol.

cifs_root_data() will be responsible to retrieve the parsed
information of the new command-line option (cifsroot=) and then call
do_mount_root() with the appropriate mount options for cifs.ko.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paulo Alcantara (SUSE) <paulo@paulo.ac>
---
 init/do_mounts.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 2d1ea3028454..28c5b583afef 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -212,6 +212,7 @@ static int match_dev_by_label(struct device *dev, const void *data)
  *	   a colon.
  *	9) PARTLABEL=<name> with name being the GPT partition label.
  *	   MSDOS partitions do not support labels!
+ *	10) /dev/cifs represents Root_CIFS (0xfe)
  *
  *	If name doesn't have fall into the categories above, we return (0,0).
  *	block_class is used to check if something is a disk name. If the disk
@@ -268,6 +269,9 @@ dev_t name_to_dev_t(const char *name)
 	res = Root_NFS;
 	if (strcmp(name, "nfs") == 0)
 		goto done;
+	res = Root_CIFS;
+	if (strcmp(name, "cifs") == 0)
+		goto done;
 	res = Root_RAM0;
 	if (strcmp(name, "ram") == 0)
 		goto done;
@@ -501,6 +505,42 @@ static int __init mount_nfs_root(void)
 }
 #endif
 
+#ifdef CONFIG_CIFS_ROOT
+
+extern int cifs_root_data(char **dev, char **opts);
+
+#define CIFSROOT_TIMEOUT_MIN	5
+#define CIFSROOT_TIMEOUT_MAX	30
+#define CIFSROOT_RETRY_MAX	5
+
+static int __init mount_cifs_root(void)
+{
+	char *root_dev, *root_data;
+	unsigned int timeout;
+	int try, err;
+
+	err = cifs_root_data(&root_dev, &root_data);
+	if (err != 0)
+		return 0;
+
+	timeout = CIFSROOT_TIMEOUT_MIN;
+	for (try = 1; ; try++) {
+		err = do_mount_root(root_dev, "cifs", root_mountflags,
+				    root_data);
+		if (err == 0)
+			return 1;
+		if (try > CIFSROOT_RETRY_MAX)
+			break;
+
+		ssleep(timeout);
+		timeout <<= 1;
+		if (timeout > CIFSROOT_TIMEOUT_MAX)
+			timeout = CIFSROOT_TIMEOUT_MAX;
+	}
+	return 0;
+}
+#endif
+
 #if defined(CONFIG_BLK_DEV_RAM) || defined(CONFIG_BLK_DEV_FD)
 void __init change_floppy(char *fmt, ...)
 {
@@ -542,6 +582,15 @@ void __init mount_root(void)
 		ROOT_DEV = Root_FD0;
 	}
 #endif
+#ifdef CONFIG_CIFS_ROOT
+	if (ROOT_DEV == Root_CIFS) {
+		if (mount_cifs_root())
+			return;
+
+		printk(KERN_ERR "VFS: Unable to mount root fs via SMB, trying floppy.\n");
+		ROOT_DEV = Root_FD0;
+	}
+#endif
 #ifdef CONFIG_BLK_DEV_FD
 	if (MAJOR(ROOT_DEV) == FLOPPY_MAJOR) {
 		/* rd_doload is 2 for a dual initrd/ramload setup */
-- 
2.22.0


^ permalink raw reply	[flat|nested] 3+ messages in thread

* [PATCH 3/3] ipconfig: Handle CONFIG_CIFS_ROOT option
  2019-07-16 22:04 [PATCH 1/3] cifs: Add support for root file systems Paulo Alcantara (SUSE)
  2019-07-16 22:04 ` [PATCH 2/3] init: Support mounting root file systems over SMB Paulo Alcantara (SUSE)
@ 2019-07-16 22:04 ` Paulo Alcantara (SUSE)
  1 sibling, 0 replies; 3+ messages in thread
From: Paulo Alcantara (SUSE) @ 2019-07-16 22:04 UTC (permalink / raw)
  To: linux-kernel, netdev, linux-cifs, samba-technical
  Cc: Paulo Alcantara (SUSE),
	David S. Miller, Alexey Kuznetsov, Hideaki YOSHIFUJI

The experimental root file system support in cifs.ko relies on
ipconfig to set up the network stack and then accessing the SMB share
that contains the rootfs files.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Signed-off-by: Paulo Alcantara (SUSE) <paulo@paulo.ac>
---
 net/ipv4/ipconfig.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index 9bcca08efec9..32e20b758b68 100644
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -1483,10 +1483,10 @@ static int __init ip_auto_config(void)
 	 * missing values.
 	 */
 	if (ic_myaddr == NONE ||
-#ifdef CONFIG_ROOT_NFS
+#if defined(CONFIG_ROOT_NFS) || defined(CONFIG_CIFS_ROOT)
 	    (root_server_addr == NONE &&
 	     ic_servaddr == NONE &&
-	     ROOT_DEV == Root_NFS) ||
+	     (ROOT_DEV == Root_NFS || ROOT_DEV == Root_CIFS)) ||
 #endif
 	    ic_first_dev->next) {
 #ifdef IPCONFIG_DYNAMIC
@@ -1513,6 +1513,12 @@ static int __init ip_auto_config(void)
 				goto try_try_again;
 			}
 #endif
+#ifdef CONFIG_CIFS_ROOT
+			if (ROOT_DEV == Root_CIFS) {
+				pr_err("IP-Config: Retrying forever (CIFS root)...\n");
+				goto try_try_again;
+			}
+#endif
 
 			if (--retries) {
 				pr_err("IP-Config: Reopening network devices...\n");
-- 
2.22.0


^ permalink raw reply	[flat|nested] 3+ messages in thread

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Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-16 22:04 [PATCH 1/3] cifs: Add support for root file systems Paulo Alcantara (SUSE)
2019-07-16 22:04 ` [PATCH 2/3] init: Support mounting root file systems over SMB Paulo Alcantara (SUSE)
2019-07-16 22:04 ` [PATCH 3/3] ipconfig: Handle CONFIG_CIFS_ROOT option Paulo Alcantara (SUSE)

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