Re: About mounting the sysfs
2007/12/18, Jan Engelhardt <[EMAIL PROTECTED]>:
>
> On Dec 18 2007 15:10, wit wrote:
> >
> >1. What is the d_alloc_root used for? Actually, the question should
> >be: why we have to call d_alloc_root.
>
> >I think the root already has its dentry,
>
> It does not.
There's no dentry for the "/"? I mean the rootfs.
>
> >why we have to allocate another while we mounting a file
> >system?
> >
> >2. Why we call d_alloc_root to allocate a dentry for the mount point
> >while the usual mount point of sysfs is defined by the user (something
> >like /sysfs but not /).
>
> /sys is a dentry that belongs to the / vfsmount, but we need a
> / that belongs to the vfsmount.
Why we need such a vfsmount (for the "/", not the rootfs)? And where
we store the mount point info (path) when mount_root, s_root and the
mnt_mountpoint are all points to the "/" which is allocated by
d_alloc_root? Or do we have to store such info? Why?
>
> > See below:
> > root = d_alloc_root(inode);
> > if (!root) {
> > pr_debug("%s: could not get root dentry!\n",__FUNCTION__);
> > iput(inode);
> > return -ENOMEM;
> > }
> > root->d_fsdata = _root;
> > sb->s_root = root;
> >
> >does this means settting the sysfs' mount point to "/" but not "/sysfs".
>
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Re: About mounting the sysfs
2007/12/18, Jan Engelhardt [EMAIL PROTECTED]:
On Dec 18 2007 15:10, wit wrote:
1. What is the d_alloc_root used for? Actually, the question should
be: why we have to call d_alloc_root.
I think the root already has its dentry,
It does not.
There's no dentry for the /? I mean the rootfs.
why we have to allocate another while we mounting a file
system?
2. Why we call d_alloc_root to allocate a dentry for the mount point
while the usual mount point of sysfs is defined by the user (something
like /sysfs but not /).
/sys is a dentry that belongs to the / vfsmount, but we need a
/ that belongs to the whatever you are going to mount vfsmount.
Why we need such a vfsmount (for the /, not the rootfs)? And where
we store the mount point info (path) when mount_root, s_root and the
mnt_mountpoint are all points to the / which is allocated by
d_alloc_root? Or do we have to store such info? Why?
See below:
root = d_alloc_root(inode);
if (!root) {
pr_debug(%s: could not get root dentry!\n,__FUNCTION__);
iput(inode);
return -ENOMEM;
}
root-d_fsdata = sysfs_root;
sb-s_root = root;
does this means settting the sysfs' mount point to / but not /sysfs.
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