[adding linux-fsdevel]
Hi Mark!
There was a question on this thread earlier about whether it makes sense
to support this in-kernel or make users build an initrd. This looks
pretty simple to me and is certainly easier for users, so (with some
adjustments) I'm happy with it, but I think the folks on
linux-fsdevel may have a more informed opinion than do.
See below for a few comments...
On Wed, 20 Nov 2013, mark.doffman@xxxxxxxxxxxxxxx wrote:
> From: Mark Doffman <mark.doffman@xxxxxxxxxxxxxxx>
>
> Analogous to NFS add a new root device option, the ability
> to boot using the Ceph networked file system as the root fs.
>
> This patch adds a new root device option '/dev/ceph' that
> uses a ceph networked file system. File system parameters
> are passed using a new kernel parameter: 'cephroot'.
>
> The 'cephroot' parameters are very similar to 'nfsroot'.
>
> Signed-off-by: Mark Doffman <mark.doffman@xxxxxxxxxxxxxxx>
> Reviewed-by: Ian Molton <ian.molton@xxxxxxxxxxxxxxx>
> ---
> fs/ceph/Kconfig | 10 +++
> fs/ceph/Makefile | 1 +
> fs/ceph/root.c | 163 +++++++++++++++++++++++++++++++++++++++++
> include/linux/ceph/ceph_root.h | 10 +++
> include/linux/root_dev.h | 1 +
> init/do_mounts.c | 32 +++++++-
> 6 files changed, 216 insertions(+), 1 deletion(-)
> create mode 100644 fs/ceph/root.c
> create mode 100644 include/linux/ceph/ceph_root.h
>
> diff --git a/fs/ceph/Kconfig b/fs/ceph/Kconfig
> index ac9a2ef..325e83d 100644
> --- a/fs/ceph/Kconfig
> +++ b/fs/ceph/Kconfig
> @@ -25,3 +25,13 @@ config CEPH_FSCACHE
> caching support for Ceph clients using FS-Cache
>
> endif
> +
> +config ROOT_CEPH
> + bool "Root file system on Ceph FS"
> + depends on CEPH_FS=y && IP_PNP
> + help
> + If you want your system to mount its root file system via CEPH,
> + choose Y here. For details, read
> + <file:Documentation/filesystems/ceph/cephroot.txt>.
> +
> + If unsure say N.
> diff --git a/fs/ceph/Makefile b/fs/ceph/Makefile
> index 32e3010..af2dcbf 100644
> --- a/fs/ceph/Makefile
> +++ b/fs/ceph/Makefile
> @@ -10,3 +10,4 @@ ceph-y := super.o inode.o dir.o file.o locks.o addr.o ioctl.o \
> debugfs.o
>
> ceph-$(CONFIG_CEPH_FSCACHE) += cache.o
> +ceph-$(CONFIG_ROOT_CEPH) += root.o
> diff --git a/fs/ceph/root.c b/fs/ceph/root.c
> new file mode 100644
> index 0000000..bff67fb
> --- /dev/null
> +++ b/fs/ceph/root.c
> @@ -0,0 +1,163 @@
> +/*
> + * Copyright (C) 2012 Codethink Ltd. <mark.doffman@xxxxxxxxxxxxxxx>
> + *
> + * This file is released under the GPL v2
> + *
> + * Allow a CephFS filesystem to be mounted as root.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/types.h>
> +#include <linux/string.h>
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/utsname.h>
> +#include <linux/root_dev.h>
> +#include <linux/in.h>
> +#include <net/ipconfig.h>
> +#include <linux/ceph/ceph_root.h>
> +
> +/* linux/net/ipv4/ipconfig.c: trims ip addr off front of name, too. */
> +extern __be32 root_nfs_parse_addr(char *name); /*__init*/
> +
> +#define MAXPATHLEN 1024
> +
> +/* Parameters passed from the kernel command line */
> +static char ceph_root_params[256] __initdata;
> +
> +/* Address of CEPH server */
> +static __be32 servaddr __initdata = htonl(INADDR_NONE);
IPv4 only?
> +
> +/* Name of directory to mount */
> +static char ceph_export_path[MAXPATHLEN + 1] __initdata;
> +
> +/* Text-based mount options */
> +static char ceph_root_options[256] __initdata;
> +
> +/* server:path string passed to mount */
> +static char ceph_root_device[MAXPATHLEN + 1] __initdata;
> +
> +/* Address of CEPH server */
> +static __be32 root_ceph_server_addr = htonl(INADDR_NONE);
> +
> +/*
> + * Parse out root export path and mount options from
> + * passed-in string @incoming.
> + *
> + * Copy the export path into @exppath.
> + *
> + * Returns 0 on success -E2BIG if the resulting options string is too long.
> + */
> +static int __init root_ceph_parse_options(char *incoming, char *exppath,
> + const size_t exppathlen)
> +{
> + char *p;
> + int res = 0;
> +
> + /*
> + * Set the remote path
> + */
> + p = strsep(&incoming, ",");
> + if (*p != '\0' && strcmp(p, "default") != 0)
> + strlcpy(exppath, p, exppathlen);
> +
> + /*
> + * @incoming now points to the rest of the string; if it
> + * contains something, append it to our root options buffer
> + */
> + if (incoming != NULL && *incoming != '\0') {
> + size_t len = strlen(ceph_root_options);
> + size_t destlen = sizeof(ceph_root_options);
> +
> + if (len && ceph_root_options[len - 1] != ',') {
> + if (strlcat(ceph_root_options, ",", destlen) > destlen)
> + res = -E2BIG;
> + }
> +
> + if (strlcat(ceph_root_options, incoming, destlen) > destlen)
> + res = -E2BIG;
> +
> + }
> + return res;
> +}
> +
> +/*
> + * Parse CephFS server and directory information passed on the kernel
> + * command line.
> + *
> + * cephroot=[<server-ip>:]<root-dir>[,<cephfs-options>]
> + */
I think we would be better off using the parsing code in fs/ceph/super.c,
which handles both IPv4 and IPv6, and more importantly lets you provide a
list of monitors. Providing only a single server IP makes it a single
point of failure during mount (though of course if/when we connect we will
discover the current set of mons).
Attaching the options at the end doesn't appeal to me cosmetically, but I
can see how it's useful to have it all in a single string that DHCP can
provide.
sage
> +static int __init ceph_root_setup(char *line)
> +{
> + ROOT_DEV = Root_CEPH;
> +
> + strlcpy(ceph_root_params, line, sizeof(ceph_root_params));
> +
> + /*
> + * Note: root_nfs_parse_addr() removes the server-ip from
> + * ceph_root_params, if it exists.
> + */
> + root_ceph_server_addr = root_nfs_parse_addr(ceph_root_params);
> +
> + return 1;
> +}
> +
> +__setup("cephroot=", ceph_root_setup);
> +
> +/*
> + * ceph_root_data - Return mount device and data for CEPHROOT mount.
> + *
> + * @root_device: OUT: Address of string containing CEPHROOT device.
> + * @root_data: OUT: Address of string containing CEPHROOT mount options.
> + *
> + * Returns: 0 and sets @root_device and @root_data if successful.
> + * error code if unsuccessful.
> + */
> +int __init ceph_root_data(char **root_device, char **root_data)
> +{
> + char *tmp = NULL;
> + const size_t tmplen = sizeof(ceph_export_path);
> + int len;
> + int ret = -E2BIG;
> +
> + servaddr = root_ceph_server_addr;
> + if (servaddr == htonl(INADDR_NONE))
> + return -ENOENT;
> +
> + tmp = kzalloc(tmplen, GFP_KERNEL);
> + if (tmp == NULL)
> + return -ENOMEM;
> +
> + if (ceph_root_params[0] != '\0') {
> + if (root_ceph_parse_options(ceph_root_params, tmp, tmplen))
> + goto out;
> + }
> +
> + /*
> + * Set up ceph_root_device. This looks like: server:/path
> + *
> + * At this point, utsname()->nodename contains our local
> + * IP address or hostname, set by ipconfig. If "%s" exists
> + * in tmp, substitute the nodename, then shovel the whole
> + * mess into ceph_root_device.
> + */
> + len = snprintf(ceph_export_path, sizeof(ceph_export_path),
> + tmp, utsname()->nodename);
> + if (len > (int)sizeof(ceph_export_path))
> + goto out;
> + len = snprintf(ceph_root_device, sizeof(ceph_root_device),
> + "%pI4:%s", &servaddr, ceph_export_path);
> + if (len > (int)sizeof(ceph_root_device))
> + goto out;
> +
> + pr_debug("Root-CEPH: Root device: %s\n", ceph_root_device);
> + pr_debug("Root-CEPH: Root options: %s\n", ceph_root_options);
> + *root_device = ceph_root_device;
> + *root_data = ceph_root_options;
> +
> + ret = 0;
> +
> +out:
> + kfree(tmp);
> + return ret;
> +}
> diff --git a/include/linux/ceph/ceph_root.h b/include/linux/ceph/ceph_root.h
> new file mode 100644
> index 0000000..e6bae63
> --- /dev/null
> +++ b/include/linux/ceph/ceph_root.h
> @@ -0,0 +1,10 @@
> +/*
> + * Copyright (C) 2012 Codethink Ltd. <mark.doffman@xxxxxxxxxxxxxxx>
> + *
> + * This file is released under the GPL v2
> + *
> + * ceph_root.h
> + */
> +
> +/* linux/fs/ceph/root.c */
> +extern int ceph_root_data(char **root_device, char **root_data); /*__init*/
> diff --git a/include/linux/root_dev.h b/include/linux/root_dev.h
> index ed241aa..af6b182 100644
> --- a/include/linux/root_dev.h
> +++ b/include/linux/root_dev.h
> @@ -16,6 +16,7 @@ enum {
> Root_SDA2 = MKDEV(SCSI_DISK0_MAJOR, 2),
> Root_HDC1 = MKDEV(IDE1_MAJOR, 1),
> Root_SR0 = MKDEV(SCSI_CDROM_MAJOR, 0),
> + Root_CEPH = MKDEV(UNNAMED_MAJOR, 254),
> };
>
> extern dev_t ROOT_DEV;
> diff --git a/init/do_mounts.c b/init/do_mounts.c
> index 8e5addc..d075020 100644
> --- a/init/do_mounts.c
> +++ b/init/do_mounts.c
> @@ -33,6 +33,8 @@
> #include <linux/nfs_fs_sb.h>
> #include <linux/nfs_mount.h>
>
> +#include <linux/ceph/ceph_root.h>
> +
> #include "do_mounts.h"
>
> int __initdata rd_doload; /* 1 = load RAM disk, 0 = don't load */
> @@ -199,6 +201,7 @@ done:
> * a partition with a known unique id.
> * 8) <major>:<minor> major and minor number of the device separated by
> * a colon.
> + * 9) /dev/ceph represents Root_CEPH
> *
> * 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
> @@ -245,7 +248,9 @@ dev_t name_to_dev_t(char *name)
> res = Root_RAM0;
> if (strcmp(name, "ram") == 0)
> goto done;
> -
> + res = Root_CEPH;
> + if (strcmp(name, "ceph") == 0)
> + goto done;
> if (strlen(name) > 31)
> goto fail;
> strcpy(s, name);
> @@ -473,6 +478,22 @@ static int __init mount_nfs_root(void)
> }
> #endif
>
> +#ifdef CONFIG_ROOT_CEPH
> +static int __init mount_ceph_root(void)
> +{
> + char *root_dev, *root_data;
> +
> + if (ceph_root_data(&root_dev, &root_data))
> + return 0;
> +
> + if (do_mount_root(root_dev, "ceph",
> + root_mountflags, root_data))
> + return 0;
> +
> + return 1;
> +}
> +#endif
> +
> #if defined(CONFIG_BLK_DEV_RAM) || defined(CONFIG_BLK_DEV_FD)
> void __init change_floppy(char *fmt, ...)
> {
> @@ -514,6 +535,15 @@ void __init mount_root(void)
> ROOT_DEV = Root_FD0;
> }
> #endif
> +#ifdef CONFIG_ROOT_CEPH
> + if (ROOT_DEV == Root_CEPH) {
> + if (mount_ceph_root())
> + return;
> +
> + printk(KERN_ERR "VFS: Unable to mount root fs via CephFS, 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 */
> --
> 1.8.4
>
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