Recovery option can be used to define a secondary rootfs
in case mounting of the primary root fails. While it has
been possible to solve the issue via bootloader and/or
initrd means, this solution is suitable for systems that
want to stay bootloader agnostic and operate without an
initrd.
Signed-off-by: Janne Karhunen <Janne.Karhunen@xxxxxxxxx>
---
Documentation/kernel-parameters.txt | 3 ++
init/do_mounts.c | 64 +++++++++++++++++++++++++++++--------
2 files changed, 54 insertions(+), 13 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 742f69d..0d65a63 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3390,6 +3390,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
nocompress Don't compress/decompress hibernation images.
no Disable hibernation and resume.
+ recovery= [KNL] Recovery root filesystem. This partition is attempted as
+ root in case default root filesystem does not mount.
+
retain_initrd [RAM] Keep initrd memory after extraction
rfkill.default_state=
diff --git a/init/do_mounts.c b/init/do_mounts.c
index dea5de9..994b2e5 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -39,8 +39,11 @@ int __initdata rd_doload; /* 1 = load RAM disk, 0 = don't load */
int root_mountflags = MS_RDONLY | MS_SILENT;
static char * __initdata root_device_name;
+static char * __initdata recovery_device_name;
static char __initdata saved_root_name[64];
+static char __initdata saved_recovery_name[64];
static int root_wait;
+static int recovery_attempt;
dev_t ROOT_DEV;
@@ -298,6 +301,15 @@ static int __init root_dev_setup(char *line)
__setup("root=", root_dev_setup);
+static int __init recovery_setup(char *line)
+{
+ strlcpy(saved_recovery_name, line, sizeof(saved_recovery_name));
+ recovery_attempt = 1;
+ return 1;
+}
+
+__setup("recovery=", recovery_setup);
+
static int __init rootwait_setup(char *str)
{
if (*str)
@@ -384,6 +396,7 @@ void __init mount_block_root(char *name, int flags)
__GFP_NOTRACK_FALSE_POSITIVE);
char *fs_names = page_address(page);
char *p;
+ int err;
#ifdef CONFIG_BLOCK
char b[BDEVNAME_SIZE];
#else
@@ -393,7 +406,7 @@ void __init mount_block_root(char *name, int flags)
get_fs_names(fs_names);
retry:
for (p = fs_names; *p; p += strlen(p)+1) {
- int err = do_mount_root(name, p, flags, root_mount_data);
+ err = do_mount_root(name, p, flags, root_mount_data);
switch (err) {
case 0:
goto out;
@@ -401,7 +414,33 @@ retry:
case -EINVAL:
continue;
}
- /*
+ if (!(flags & MS_RDONLY)) {
+ pr_warn("Retrying rootfs mount as read-only.\n");
+ flags |= MS_RDONLY;
+ goto retry;
+ }
+ if (recovery_device_name && recovery_attempt) {
+ recovery_attempt = 0;
+
+ ROOT_DEV = name_to_dev_t(recovery_device_name);
+ if (strncmp(recovery_device_name, "/dev/", 5) == 0)
+ recovery_device_name += 5;
+
+ pr_warn("Unable to mount rootfs at %s, error %d.\n",
+ root_device_name, err);
+ pr_warn("Attempting %s for recovery as requested.\n",
+ recovery_device_name);
+
+ err = create_dev("/dev/root", ROOT_DEV);
+ if (err < 0)
+ pr_emerg("Failed to re-create /dev/root: %d\n",
+ err);
+
+ root_device_name = recovery_device_name;
+ goto retry;
+ }
+
+ /*
* Allow the user to distinguish between failed sys_open
* and bad superblock on root device.
* and give them a list of the available devices
@@ -409,28 +448,24 @@ retry:
#ifdef CONFIG_BLOCK
__bdevname(ROOT_DEV, b);
#endif
- printk("VFS: Cannot open root device \"%s\" or %s: error %d\n",
+ pr_emerg("VFS: Cannot open root device \"%s\" or %s: error %d\n",
root_device_name, b, err);
- printk("Please append a correct \"root=\" boot option; here are the available partitions:\n");
+ pr_emerg("Please append a correct \"root=\" boot option; here are the available partitions:\n");
printk_all_partitions();
#ifdef CONFIG_DEBUG_BLOCK_EXT_DEVT
- printk("DEBUG_BLOCK_EXT_DEVT is enabled, you need to specify "
+ pr_emerg("DEBUG_BLOCK_EXT_DEVT is enabled, you need to specify "
"explicit textual name for \"root=\" boot option.\n");
#endif
panic("VFS: Unable to mount root fs on %s", b);
}
- if (!(flags & MS_RDONLY)) {
- flags |= MS_RDONLY;
- goto retry;
- }
- printk("List of all partitions:\n");
+ pr_emerg("List of all partitions:\n");
printk_all_partitions();
- printk("No filesystem could mount root, tried: ");
+ pr_emerg("No filesystem could mount root, tried: ");
for (p = fs_names; *p; p += strlen(p)+1)
- printk(" %s", p);
- printk("\n");
+ pr_emerg(" %s", p);
+ pr_emerg("\n");
#ifdef CONFIG_BLOCK
__bdevname(ROOT_DEV, b);
#endif
@@ -567,6 +602,9 @@ void __init prepare_namespace(void)
md_run_setup();
+ if (saved_recovery_name[0])
+ recovery_device_name = saved_recovery_name;
+
if (saved_root_name[0]) {
root_device_name = saved_root_name;
if (!strncmp(root_device_name, "mtd", 3) ||
--
1.9.1
--
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