CHROMIUM: dm: boot time specification of dm=

This is a wrap-up of three patches pending upstream approval.
I'm bundling them because they are interdependent, and it'll be
easier to drop it on rebase later.

1. dm: allow a dm-fs-style device to be shared via dm-ioctl

Integrates feedback from Alisdair, Mike, and Kiyoshi.

Two main changes occur here:

- One function is added which allows for a programmatically created
mapped device to be inserted into the dm-ioctl hash table.  This binds
the device to a name and, optional, uuid which is needed by udev and
allows for userspace management of the mapped device.

- dm_table_complete() was extended to handle all of the final
functional changes required for the table to be operational once
called.

2. init: boot to device-mapper targets without an initr*

Add a dm= kernel parameter modeled after the md= parameter from
do_mounts_md.  It allows for device-mapper targets to be configured at
boot time for use early in the boot process (as the root device or
otherwise).  It also replaces /dev/XXX calls with major:minor opportunistically.

The format is dm="name uuid ro,table line 1,table line 2,...".  The
parser expects the comma to be safe to use as a newline substitute but,
otherwise, uses the normal separator of space.  Some attempt has been
made to make it forgiving of additional spaces (using skip_spaces()).

A mapped device created during boot will be assigned a minor of 0 and
may be access via /dev/dm-0.

An example dm-linear root with no uuid may look like:

root=/dev/dm-0  dm="lroot none ro, 0 4096 linear /dev/ubdb 0, 4096 4096 linear /dv/ubdc 0"

Once udev is started, /dev/dm-0 will become /dev/mapper/lroot.

Older upstream threads:
http://marc.info/?l=dm-devel&m=127429492521964&w=2
http://marc.info/?l=dm-devel&m=127429499422096&w=2
http://marc.info/?l=dm-devel&m=127429493922000&w=2

Latest upstream threads:
https://patchwork.kernel.org/patch/104859/
https://patchwork.kernel.org/patch/104860/
https://patchwork.kernel.org/patch/104861/

Bug: 27175947

Signed-off-by: Will Drewry <wad@chromium.org>

Review URL: http://codereview.chromium.org/2020011

Change-Id: I92bd53432a11241228d2e5ac89a3b20d19b05a31

[AmitP: Refactored the original changes based on upstream changes,
        commit e52347bd66 ("Documentation/admin-guide: split the kernel parameter list to a separate file")]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
This commit is contained in:
Will Drewry 2010-06-09 17:47:38 -05:00 committed by Amit Pundir
parent 8fe0ca37c8
commit ee3ad542dd
9 changed files with 513 additions and 0 deletions

View File

@ -880,6 +880,9 @@
dis_ucode_ldr [X86] Disable the microcode loader.
dm= [DM] Allows early creation of a device-mapper device.
See Documentation/device-mapper/boot.txt.
dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
this option disables the debugging code at boot.

View File

@ -0,0 +1,42 @@
Boot time creation of mapped devices
===================================
It is possible to configure a device mapper device to act as the root
device for your system in two ways.
The first is to build an initial ramdisk which boots to a minimal
userspace which configures the device, then pivot_root(8) in to it.
For simple device mapper configurations, it is possible to boot directly
using the following kernel command line:
dm="<name> <uuid> <ro>,table line 1,...,table line n"
name = the name to associate with the device
after boot, udev, if used, will use that name to label
the device node.
uuid = may be 'none' or the UUID desired for the device.
ro = may be "ro" or "rw". If "ro", the device and device table will be
marked read-only.
Each table line may be as normal when using the dmsetup tool except for
two variations:
1. Any use of commas will be interpreted as a newline
2. Quotation marks cannot be escaped and cannot be used without
terminating the dm= argument.
Unless renamed by udev, the device node created will be dm-0 as the
first minor number for the device-mapper is used during early creation.
Example
=======
- Booting to a linear array made up of user-mode linux block devices:
dm="lroot none 0, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" \
root=/dev/dm-0
Will boot to a rw dm-linear target of 8192 sectors split across two
block devices identified by their major:minor numbers. After boot, udev
will rename this target to /dev/mapper/lroot (depending on the rules).
No uuid was assigned.

View File

@ -1993,6 +1993,45 @@ void dm_interface_exit(void)
dm_hash_exit();
}
/**
* dm_ioctl_export - Permanently export a mapped device via the ioctl interface
* @md: Pointer to mapped_device
* @name: Buffer (size DM_NAME_LEN) for name
* @uuid: Buffer (size DM_UUID_LEN) for uuid or NULL if not desired
*/
int dm_ioctl_export(struct mapped_device *md, const char *name,
const char *uuid)
{
int r = 0;
struct hash_cell *hc;
if (!md) {
r = -ENXIO;
goto out;
}
/* The name and uuid can only be set once. */
mutex_lock(&dm_hash_cells_mutex);
hc = dm_get_mdptr(md);
mutex_unlock(&dm_hash_cells_mutex);
if (hc) {
DMERR("%s: already exported", dm_device_name(md));
r = -ENXIO;
goto out;
}
r = dm_hash_insert(name, uuid, md);
if (r) {
DMERR("%s: could not bind to '%s'", dm_device_name(md), name);
goto out;
}
/* Let udev know we've changed. */
dm_kobject_uevent(md, KOBJ_CHANGE, dm_get_event_nr(md));
out:
return r;
}
/**
* dm_copy_name_and_uuid - Copy mapped device name & uuid into supplied buffers
* @md: Pointer to mapped_device

View File

@ -11,6 +11,7 @@
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/slab.h>

View File

@ -397,6 +397,12 @@ void dm_put(struct mapped_device *md);
void dm_set_mdptr(struct mapped_device *md, void *ptr);
void *dm_get_mdptr(struct mapped_device *md);
/*
* Export the device via the ioctl interface (uses mdptr).
*/
int dm_ioctl_export(struct mapped_device *md, const char *name,
const char *uuid);
/*
* A device can still be used while suspended, but I/O is deferred.
*/

View File

@ -19,6 +19,7 @@ mounts-y := do_mounts.o
mounts-$(CONFIG_BLK_DEV_RAM) += do_mounts_rd.o
mounts-$(CONFIG_BLK_DEV_INITRD) += do_mounts_initrd.o
mounts-$(CONFIG_BLK_DEV_MD) += do_mounts_md.o
mounts-$(CONFIG_BLK_DEV_DM) += do_mounts_dm.o
# dependencies on generated files need to be listed explicitly
$(obj)/version.o: include/generated/compile.h

View File

@ -555,6 +555,7 @@ void __init prepare_namespace(void)
wait_for_device_probe();
md_run_setup();
dm_run_setup();
if (saved_root_name[0]) {
root_device_name = saved_root_name;

View File

@ -61,3 +61,13 @@ void md_run_setup(void);
static inline void md_run_setup(void) {}
#endif
#ifdef CONFIG_BLK_DEV_DM
void dm_run_setup(void);
#else
static inline void dm_run_setup(void) {}
#endif

410
init/do_mounts_dm.c Normal file
View File

@ -0,0 +1,410 @@
/* do_mounts_dm.c
* Copyright (C) 2010 The Chromium OS Authors <chromium-os-dev@chromium.org>
* All Rights Reserved.
* Based on do_mounts_md.c
*
* This file is released under the GPL.
*/
#include <linux/device-mapper.h>
#include <linux/fs.h>
#include <linux/string.h>
#include "do_mounts.h"
#define DM_MAX_NAME 32
#define DM_MAX_UUID 129
#define DM_NO_UUID "none"
#define DM_MSG_PREFIX "init"
/* Separators used for parsing the dm= argument. */
#define DM_FIELD_SEP ' '
#define DM_LINE_SEP ','
/*
* When the device-mapper and any targets are compiled into the kernel
* (not a module), one target may be created and used as the root device at
* boot time with the parameters given with the boot line dm=...
* The code for that is here.
*/
struct dm_setup_target {
sector_t begin;
sector_t length;
char *type;
char *params;
/* simple singly linked list */
struct dm_setup_target *next;
};
static struct {
int minor;
int ro;
char name[DM_MAX_NAME];
char uuid[DM_MAX_UUID];
char *targets;
struct dm_setup_target *target;
int target_count;
} dm_setup_args __initdata;
static __initdata int dm_early_setup;
static size_t __init get_dm_option(char *str, char **next, char sep)
{
size_t len = 0;
char *endp = NULL;
if (!str)
return 0;
endp = strchr(str, sep);
if (!endp) { /* act like strchrnul */
len = strlen(str);
endp = str + len;
} else {
len = endp - str;
}
if (endp == str)
return 0;
if (!next)
return len;
if (*endp == 0) {
/* Don't advance past the nul. */
*next = endp;
} else {
*next = endp + 1;
}
return len;
}
static int __init dm_setup_args_init(void)
{
dm_setup_args.minor = 0;
dm_setup_args.ro = 0;
dm_setup_args.target = NULL;
dm_setup_args.target_count = 0;
return 0;
}
static int __init dm_setup_cleanup(void)
{
struct dm_setup_target *target = dm_setup_args.target;
struct dm_setup_target *old_target = NULL;
while (target) {
kfree(target->type);
kfree(target->params);
old_target = target;
target = target->next;
kfree(old_target);
dm_setup_args.target_count--;
}
BUG_ON(dm_setup_args.target_count);
return 0;
}
static char * __init dm_setup_parse_device_args(char *str)
{
char *next = NULL;
size_t len = 0;
/* Grab the logical name of the device to be exported to udev */
len = get_dm_option(str, &next, DM_FIELD_SEP);
if (!len) {
DMERR("failed to parse device name");
goto parse_fail;
}
len = min(len + 1, sizeof(dm_setup_args.name));
strlcpy(dm_setup_args.name, str, len); /* includes nul */
str = skip_spaces(next);
/* Grab the UUID value or "none" */
len = get_dm_option(str, &next, DM_FIELD_SEP);
if (!len) {
DMERR("failed to parse device uuid");
goto parse_fail;
}
len = min(len + 1, sizeof(dm_setup_args.uuid));
strlcpy(dm_setup_args.uuid, str, len);
str = skip_spaces(next);
/* Determine if the table/device will be read only or read-write */
if (!strncmp("ro,", str, 3)) {
dm_setup_args.ro = 1;
} else if (!strncmp("rw,", str, 3)) {
dm_setup_args.ro = 0;
} else {
DMERR("failed to parse table mode");
goto parse_fail;
}
str = skip_spaces(str + 3);
return str;
parse_fail:
return NULL;
}
static void __init dm_substitute_devices(char *str, size_t str_len)
{
char *candidate = str;
char *candidate_end = str;
char old_char;
size_t len = 0;
dev_t dev;
if (str_len < 3)
return;
while (str && *str) {
candidate = strchr(str, '/');
if (!candidate)
break;
/* Avoid embedded slashes */
if (candidate != str && *(candidate - 1) != DM_FIELD_SEP) {
str = strchr(candidate, DM_FIELD_SEP);
continue;
}
len = get_dm_option(candidate, &candidate_end, DM_FIELD_SEP);
str = skip_spaces(candidate_end);
if (len < 3 || len > 37) /* name_to_dev_t max; maj:mix min */
continue;
/* Temporarily terminate with a nul */
candidate_end--;
old_char = *candidate_end;
*candidate_end = '\0';
DMDEBUG("converting candidate device '%s' to dev_t", candidate);
/* Use the boot-time specific device naming */
dev = name_to_dev_t(candidate);
*candidate_end = old_char;
DMDEBUG(" -> %u", dev);
/* No suitable replacement found */
if (!dev)
continue;
/* Rewrite the /dev/path as a major:minor */
len = snprintf(candidate, len, "%u:%u", MAJOR(dev), MINOR(dev));
if (!len) {
DMERR("error substituting device major/minor.");
break;
}
candidate += len;
/* Pad out with spaces (fixing our nul) */
while (candidate < candidate_end)
*(candidate++) = DM_FIELD_SEP;
}
}
static int __init dm_setup_parse_targets(char *str)
{
char *next = NULL;
size_t len = 0;
struct dm_setup_target **target = NULL;
/* Targets are defined as per the table format but with a
* comma as a newline separator. */
target = &dm_setup_args.target;
while (str && *str) {
*target = kzalloc(sizeof(struct dm_setup_target), GFP_KERNEL);
if (!*target) {
DMERR("failed to allocate memory for target %d",
dm_setup_args.target_count);
goto parse_fail;
}
dm_setup_args.target_count++;
(*target)->begin = simple_strtoull(str, &next, 10);
if (!next || *next != DM_FIELD_SEP) {
DMERR("failed to parse starting sector for target %d",
dm_setup_args.target_count - 1);
goto parse_fail;
}
str = skip_spaces(next + 1);
(*target)->length = simple_strtoull(str, &next, 10);
if (!next || *next != DM_FIELD_SEP) {
DMERR("failed to parse length for target %d",
dm_setup_args.target_count - 1);
goto parse_fail;
}
str = skip_spaces(next + 1);
len = get_dm_option(str, &next, DM_FIELD_SEP);
if (!len ||
!((*target)->type = kstrndup(str, len, GFP_KERNEL))) {
DMERR("failed to parse type for target %d",
dm_setup_args.target_count - 1);
goto parse_fail;
}
str = skip_spaces(next);
len = get_dm_option(str, &next, DM_LINE_SEP);
if (!len ||
!((*target)->params = kstrndup(str, len, GFP_KERNEL))) {
DMERR("failed to parse params for target %d",
dm_setup_args.target_count - 1);
goto parse_fail;
}
str = skip_spaces(next);
/* Before moving on, walk through the copied target and
* attempt to replace all /dev/xxx with the major:minor number.
* It may not be possible to resolve them traditionally at
* boot-time. */
dm_substitute_devices((*target)->params, len);
target = &((*target)->next);
}
DMDEBUG("parsed %d targets", dm_setup_args.target_count);
return 0;
parse_fail:
return 1;
}
/*
* Parse the command-line parameters given our kernel, but do not
* actually try to invoke the DM device now; that is handled by
* dm_setup_drive after the low-level disk drivers have initialised.
* dm format is as follows:
* dm="name uuid fmode,[table line 1],[table line 2],..."
* May be used with root=/dev/dm-0 as it always uses the first dm minor.
*/
static int __init dm_setup(char *str)
{
dm_setup_args_init();
str = dm_setup_parse_device_args(str);
if (!str) {
DMDEBUG("str is NULL");
goto parse_fail;
}
/* Target parsing is delayed until we have dynamic memory */
dm_setup_args.targets = str;
printk(KERN_INFO "dm: will configure '%s' on dm-%d\n",
dm_setup_args.name, dm_setup_args.minor);
dm_early_setup = 1;
return 1;
parse_fail:
printk(KERN_WARNING "dm: Invalid arguments supplied to dm=.\n");
return 0;
}
static void __init dm_setup_drive(void)
{
struct mapped_device *md = NULL;
struct dm_table *table = NULL;
struct dm_setup_target *target;
char *uuid = dm_setup_args.uuid;
fmode_t fmode = FMODE_READ;
/* Finish parsing the targets. */
if (dm_setup_parse_targets(dm_setup_args.targets))
goto parse_fail;
if (dm_create(dm_setup_args.minor, &md)) {
DMDEBUG("failed to create the device");
goto dm_create_fail;
}
DMDEBUG("created device '%s'", dm_device_name(md));
/* In addition to flagging the table below, the disk must be
* set explicitly ro/rw. */
set_disk_ro(dm_disk(md), dm_setup_args.ro);
if (!dm_setup_args.ro)
fmode |= FMODE_WRITE;
if (dm_table_create(&table, fmode, dm_setup_args.target_count, md)) {
DMDEBUG("failed to create the table");
goto dm_table_create_fail;
}
target = dm_setup_args.target;
while (target) {
DMINFO("adding target '%llu %llu %s %s'",
(unsigned long long) target->begin,
(unsigned long long) target->length, target->type,
target->params);
if (dm_table_add_target(table, target->type, target->begin,
target->length, target->params)) {
DMDEBUG("failed to add the target to the table");
goto add_target_fail;
}
target = target->next;
}
if (dm_table_complete(table)) {
DMDEBUG("failed to complete the table");
goto table_complete_fail;
}
/* Suspend the device so that we can bind it to the table. */
if (dm_suspend(md, 0)) {
DMDEBUG("failed to suspend the device pre-bind");
goto suspend_fail;
}
/* Bind the table to the device. This is the only way to associate
* md->map with the table and set the disk capacity directly. */
if (dm_swap_table(md, table)) { /* should return NULL. */
DMDEBUG("failed to bind the device to the table");
goto table_bind_fail;
}
/* Finally, resume and the device should be ready. */
if (dm_resume(md)) {
DMDEBUG("failed to resume the device");
goto resume_fail;
}
/* Export the dm device via the ioctl interface */
if (!strcmp(DM_NO_UUID, dm_setup_args.uuid))
uuid = NULL;
if (dm_ioctl_export(md, dm_setup_args.name, uuid)) {
DMDEBUG("failed to export device with given name and uuid");
goto export_fail;
}
printk(KERN_INFO "dm: dm-%d is ready\n", dm_setup_args.minor);
dm_setup_cleanup();
return;
export_fail:
resume_fail:
table_bind_fail:
suspend_fail:
table_complete_fail:
add_target_fail:
dm_table_put(table);
dm_table_create_fail:
dm_put(md);
dm_create_fail:
dm_setup_cleanup();
parse_fail:
printk(KERN_WARNING "dm: starting dm-%d (%s) failed\n",
dm_setup_args.minor, dm_setup_args.name);
}
__setup("dm=", dm_setup);
void __init dm_run_setup(void)
{
if (!dm_early_setup)
return;
printk(KERN_INFO "dm: attempting early device configuration.\n");
dm_setup_drive();
}