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
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.
>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.
> 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
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.
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.
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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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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About mounting the sysfs
Hi all,
Currently, I'm studying the code of the sysfs. But I got the
following questions:
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, 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 /). 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".
Thanks.
--Zhanhua
--
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the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
About mounting the sysfs
Hi all,
Currently, I'm studying the code of the sysfs. But I got the
following questions:
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, 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 /). 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.
Thanks.
--Zhanhua
--
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the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
about mounting the sysfs
Hi,
I found the initialization code of the sysfs in version 2.6.22:
int __init sysfs_init(void)
{
int err = -ENOMEM;
sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
sizeof(struct sysfs_dirent),
0, 0, NULL, NULL);
if (!sysfs_dir_cachep)
goto out;
err = register_filesystem(_fs_type);
if (!err) {
sysfs_mount = kern_mount(_fs_type);
my questions are:
1. Is some initializing script responsible for mounting the sysfs? If
so, why do we call kern_mount.
2. I looked into the kern_mount code, the routine seems to get the
super block and the inode object for the sysfs, but when setting the
root, I got:
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;
and the s_root is then passed to the mnt_root and the mnt_mountpoint:
int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)
{
mnt->mnt_sb = sb;
mnt->mnt_root = dget(sb->s_root);
return 0;
}
in vfs_kern_mount:
...
mnt->mnt_mountpoint = mnt->mnt_root;
mnt->mnt_parent = mnt;
up_write(>mnt_sb->s_umount);
...
So, does this means we get the mount point from d_alloc_root(inode),
but this doesn't look like the truth. d_alloc_root seems to allocate a
dentry for the root, is that true? If so, why for the root?
Does the s_root stand for the root of the file system, so it should
always be "/", but this is different from root file system? But what
about the mnt_moountpoint, how does the kernel store the path (rooted
from the root file system)?
Thanks
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
about mounting the sysfs
Hi,
I found the initialization code of the sysfs in version 2.6.22:
int __init sysfs_init(void)
{
int err = -ENOMEM;
sysfs_dir_cachep = kmem_cache_create(sysfs_dir_cache,
sizeof(struct sysfs_dirent),
0, 0, NULL, NULL);
if (!sysfs_dir_cachep)
goto out;
err = register_filesystem(sysfs_fs_type);
if (!err) {
sysfs_mount = kern_mount(sysfs_fs_type);
my questions are:
1. Is some initializing script responsible for mounting the sysfs? If
so, why do we call kern_mount.
2. I looked into the kern_mount code, the routine seems to get the
super block and the inode object for the sysfs, but when setting the
root, I got:
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;
and the s_root is then passed to the mnt_root and the mnt_mountpoint:
int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)
{
mnt-mnt_sb = sb;
mnt-mnt_root = dget(sb-s_root);
return 0;
}
in vfs_kern_mount:
...
mnt-mnt_mountpoint = mnt-mnt_root;
mnt-mnt_parent = mnt;
up_write(mnt-mnt_sb-s_umount);
...
So, does this means we get the mount point from d_alloc_root(inode),
but this doesn't look like the truth. d_alloc_root seems to allocate a
dentry for the root, is that true? If so, why for the root?
Does the s_root stand for the root of the file system, so it should
always be /, but this is different from root file system? But what
about the mnt_moountpoint, how does the kernel store the path (rooted
from the root file system)?
Thanks
--
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the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
