[PATCH] init: Support mounting devices from kernel command line

Sasha Levin
2011-07-18T09:06:36Z

This patch adds support to mounting devices using a kernel parameter.

Such feature is usefull for virtual guests. It allows easily automating
mounts without having to change the base image (which can be read-only).

In /tools/kvm we are interested in such feature to allow us to automatically
mount user home directory using virtio-9p from the host to the guest
filesystem under '/hostfs'.

Cc: Avi Kivity <avi@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
Documentation/kernel-parameters.txt | 6 +++
init/do_mounts.c | 61 +++++++++++++++++++++++++++++++++++
2 files changed, 67 insertions(+), 0 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index aa47be7..e1955fb 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1476,6 +1476,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
log everything. Information is printed at KERN_DEBUG
so loglevel=8 may also need to be specified.

+ mount=
+ [KNL] Mount a device to a mount point after loading
+ rootfs and setting up devices. Can be used to mount
+ up to 16 devices.
+ Format: ,<destination>,<fs>[,<params>]
+
mousedev.tap_time=
[MOUSE] Maximum time between finger touching and
leaving touchpad surface for touch to be considered
diff --git a/init/do_mounts.c b/init/do_mounts.c
index c0851a8..0948f1d 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -29,9 +29,24 @@ int root_mountflags = MS_RDONLY | MS_SILENT;
static char * __initdata root_device_name;
static char __initdata saved_root_name[64];
static int __initdata root_wait;
+static char * __initdata user_mount[16];
+static int __initdata user_mount_count;

dev_t ROOT_DEV;

+static int __init setup_user_mount(char *str)
+{
+ if (user_mount_count > 15) {
+ printk(KERN_ERR "More than 16 'mount=' options specified.")
+ return 1;
+ }
+
+ user_mount[user_mount_count++] = str;
+
+ return 1;
+}
+__setup("mount=", setup_user_mount);
+
static int __init load_ramdisk(char *str)
{
rd_doload = simple_strtol(str,NULL,0) & 3;
@@ -431,6 +446,51 @@ void __init mount_root(void)
#endif
}

+int __init do_user_mounts(void)
+{
+ int i, res;
+ char *src, *dst, *fs, *params, *cur;
+
+ for (i = 0; i < user_mount_count; i++) {
+ src = user_mount[i];
+ cur = strstr(user_mount[i], ",");
+ if (!cur)
+ goto fail_str;
+
+ *cur = '\0';
+ dst = ++cur;
+
+ cur = strstr(cur, ",");
+ if (!cur)
+ goto fail_str;
+
+ *cur = '\0';
+ fs = ++cur;
+
+ cur = strstr(cur, ",");
+ if (cur) {
+ *cur = '\0';
+ params = ++cur;
+ } else {
+ params = NULL;
+ }
+
+ res = sys_mount(src, dst, fs, 0, params);
+ if (res == 0)
+ printk(KERN_INFO "Mounted (%s filesystem) %s to %s\n",
+ fs, src, dst);
+ else
+ printk(KERN_ERR "Failed mounting (%s filesystem) %s to"
+ " %s. Err: %d\n", fs, src, dst, res);
+ }
+
+ return 0;
+
+fail_str:
+ printk(KERN_ERR "Bad mount str: %s\n", user_mount[i]);
+ return -1;
+}
+
/*
* Prepare the namespace - decide what/where to mount, load ramdisks, etc.
*/
@@ -490,4 +550,5 @@ out:
devtmpfs_mount("dev");
sys_mount(".", "/", NULL, MS_MOVE, NULL);
sys_chroot((const char __user __force *)".");
+ do_user_mounts();
}
--
1.7.6