On Saturday February 28, miquels@cistron.nl wrote:
>
> Hmm. With a dynamic major, the system might fail at checking the root
> file system at boot. At that time, /dev is still read-only, and
> /dev/md/d0p1 might not be the correct device yet.
>
> So either mdp needs its own partition number, or we need a /dev/root
> device that's an alias for the current root (like /dev/console).
>
Yes, I think this is a real problem.
There are a number of avenues that could be followed to fix it.
One it your suggestion.
Another is to make "rootfs" remountable like this:
--- ./fs/ramfs/inode.c~current~ 2004-03-01 11:20:58.000000000 +1100
+++ ./fs/ramfs/inode.c 2004-03-01 11:21:15.000000000 +1100
@@ -207,7 +207,7 @@ static struct super_block *ramfs_get_sb(
static struct super_block *rootfs_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
- return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super);
+ return get_sb_single(fs_type, flags, data, ramfs_fill_super);
}
static struct file_system_type ramfs_fs_type = {
And then:
mount -t rootfs rootfs /mnt/root
fsck /mnt/root/dev/root
Another is to add "rootdev" to /proc/*, as in appended patch. Then
ln -s /proc/self/roodev /dev/root
and providing /proc is mounted, /dev/root will work.
I think I prefer the /proc/self/rootdev approach despite it being the
bigger patch.
I might try to push it on linux-kernel.
NeilBrown
diff ./fs/proc/base.c~current~ ./fs/proc/base.c
--- ./fs/proc/base.c~current~ 2004-03-01 11:28:24.000000000 +1100
+++ ./fs/proc/base.c 2004-03-01 11:48:07.000000000 +1100
@@ -50,6 +50,7 @@ enum pid_directory_inos {
PROC_TGID_MEM,
PROC_TGID_CWD,
PROC_TGID_ROOT,
+ PROC_TGID_ROOTDEV,
PROC_TGID_EXE,
PROC_TGID_FD,
PROC_TGID_ENVIRON,
@@ -73,6 +74,7 @@ enum pid_directory_inos {
PROC_TID_MEM,
PROC_TID_CWD,
PROC_TID_ROOT,
+ PROC_TID_ROOTDEV,
PROC_TID_EXE,
PROC_TID_FD,
PROC_TID_ENVIRON,
@@ -115,6 +117,7 @@ static struct pid_entry tgid_base_stuff[
E(PROC_TGID_MEM, "mem", S_IFREG|S_IRUSR|S_IWUSR),
E(PROC_TGID_CWD, "cwd", S_IFLNK|S_IRWXUGO),
E(PROC_TGID_ROOT, "root", S_IFLNK|S_IRWXUGO),
+ E(PROC_TGID_ROOTDEV, "rootdev", S_IFBLK|S_IRUSR|S_IWUSR),
E(PROC_TGID_EXE, "exe", S_IFLNK|S_IRWXUGO),
E(PROC_TGID_MOUNTS, "mounts", S_IFREG|S_IRUGO),
#ifdef CONFIG_SECURITY
@@ -137,6 +140,7 @@ static struct pid_entry tid_base_stuff[]
E(PROC_TID_MEM, "mem", S_IFREG|S_IRUSR|S_IWUSR),
E(PROC_TID_CWD, "cwd", S_IFLNK|S_IRWXUGO),
E(PROC_TID_ROOT, "root", S_IFLNK|S_IRWXUGO),
+ E(PROC_TID_ROOTDEV, "rootdev", S_IFBLK|S_IRUSR|S_IWUSR),
E(PROC_TID_EXE, "exe", S_IFLNK|S_IRWXUGO),
E(PROC_TID_MOUNTS, "mounts", S_IFREG|S_IRUGO),
#ifdef CONFIG_SECURITY
@@ -771,6 +775,32 @@ static struct inode_operations proc_pid_
.follow_link = proc_pid_follow_link
};
+int proc_pid_get_attr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
+{
+ struct inode *inode = dentry->d_inode;
+ struct fs_struct *fs;
+ int result = -ENOENT;
+ generic_fillattr(inode, stat);
+ task_lock(proc_task(inode));
+ fs = proc_task(inode)->fs;
+ if(fs)
+ atomic_inc(&fs->count);
+ task_unlock(proc_task(inode));
+ if (fs) {
+ read_lock(&fs->lock);
+ stat->rdev = fs->pwdmnt->mnt_sb->s_dev;
+ read_unlock(&fs->lock);
+ result = 0;
+ put_fs_struct(fs);
+ }
+
+ return result;
+}
+
+static struct inode_operations proc_pid_dev_inode_operations = {
+ .getattr = proc_pid_get_attr,
+};
+
static int pid_alive(struct task_struct *p)
{
BUG_ON(p->pids[PIDTYPE_PID].pidptr != &p->pids[PIDTYPE_PID].pid);
@@ -1319,6 +1349,10 @@ static struct dentry *proc_pident_lookup
inode->i_op = &proc_pid_link_inode_operations;
ei->op.proc_get_link = proc_root_link;
break;
+ case PROC_TID_ROOTDEV:
+ case PROC_TGID_ROOTDEV:
+ inode->i_op = &proc_pid_dev_inode_operations;
+ break;
case PROC_TID_ENVIRON:
case PROC_TGID_ENVIRON:
inode->i_fop = &proc_info_file_operations;
-
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