From: Vivek Goyal <vgoyal@redhat.com>
To: viro@zeniv.linux.org.uk
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
hch@lst.de, virtio-fs@redhat.com,
v9fs-developer@lists.sourceforge.net, stefanha@redhat.com,
miklos@szeredi.hu
Subject: [PATCH v3 2/3] init: allow mounting arbitrary non-blockdevice filesystems as root
Date: Wed, 14 Jul 2021 16:23:20 -0400 [thread overview]
Message-ID: <20210714202321.59729-3-vgoyal@redhat.com> (raw)
In-Reply-To: <20210714202321.59729-1-vgoyal@redhat.com>
From: Christoph Hellwig <hch@lst.de>
Currently the only non-blockdevice filesystems that can be used as the
initial root filesystem are NFS and CIFS, which use the magic
"root=/dev/nfs" and "root=/dev/cifs" syntax that requires the root
device file system details to come from filesystem specific kernel
command line options.
Add a little bit of new code that allows to just pass arbitrary
string mount options to any non-blockdevice filesystems so that it can
be mounted as the root file system.
For example a virtiofs root file system can be mounted using the
following syntax:
"root=myfs rootfstype=virtiofs rw"
Based on an earlier patch from Vivek Goyal <vgoyal@redhat.com>.
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
init/do_mounts.c | 43 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 43 insertions(+)
diff --git a/init/do_mounts.c b/init/do_mounts.c
index ec32de3ad52b..bdeb90b8d669 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -534,6 +534,45 @@ static int __init mount_cifs_root(void)
}
#endif
+static bool __init fs_is_nodev(char *fstype)
+{
+ struct file_system_type *fs = get_fs_type(fstype);
+ bool ret = false;
+
+ if (fs) {
+ ret = !(fs->fs_flags & FS_REQUIRES_DEV);
+ put_filesystem(fs);
+ }
+
+ return ret;
+}
+
+static int __init mount_nodev_root(void)
+{
+ char *fs_names, *fstype;
+ int err = -EINVAL;
+
+ fs_names = (void *)__get_free_page(GFP_KERNEL);
+ if (!fs_names)
+ return -EINVAL;
+ split_fs_names(fs_names, root_fs_names);
+
+ for (fstype = fs_names; *fstype; fstype += strlen(fstype) + 1) {
+ if (!fs_is_nodev(fstype))
+ continue;
+ err = do_mount_root(root_device_name, fstype, root_mountflags,
+ root_mount_data);
+ if (!err)
+ break;
+ if (err != -EACCES && err != -EINVAL)
+ panic("VFS: Unable to mount root \"%s\" (%s), err=%d\n",
+ root_device_name, fstype, err);
+ }
+
+ free_page((unsigned long)fs_names);
+ return err;
+}
+
void __init mount_root(void)
{
#ifdef CONFIG_ROOT_NFS
@@ -550,6 +589,10 @@ void __init mount_root(void)
return;
}
#endif
+ if (ROOT_DEV == 0 && root_device_name && root_fs_names) {
+ if (mount_nodev_root() == 0)
+ return;
+ }
#ifdef CONFIG_BLOCK
{
int err = create_dev("/dev/root", ROOT_DEV);
--
2.31.1
next prev parent reply other threads:[~2021-07-14 20:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-14 20:23 [PATCH v3 0/3] support booting of arbitrary non-blockdevice file systems Vivek Goyal
2021-07-14 20:23 ` [PATCH v3 1/3] init: split get_fs_names Vivek Goyal
2021-07-15 10:04 ` Stefan Hajnoczi
2021-07-14 20:23 ` Vivek Goyal [this message]
2021-07-15 10:04 ` [PATCH v3 2/3] init: allow mounting arbitrary non-blockdevice filesystems as root Stefan Hajnoczi
2021-07-14 20:23 ` [PATCH v3 3/3] fs: simplify get_filesystem_list / get_all_fs_names Vivek Goyal
2021-07-21 15:46 ` Stefan Hajnoczi
2021-07-30 0:57 ` Al Viro
2021-07-30 12:24 ` Vivek Goyal
2021-07-27 18:29 ` [PATCH v3 0/3] support booting of arbitrary non-blockdevice file systems Vivek Goyal
2021-07-29 15:08 ` Christian Brauner
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