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Date: Thu, 23 Jun 2005 09:25:36 -0700
From: Mike Waychison <mikew@google.com>
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To: cspalletta@adelphia.net
CC: linux-kernel@vger.kernel.org
Subject: Re: namespace question
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cspalletta@adelphia.net wrote:
> I don't believe the following to be an error, but I am curious how it occurs:
> 
> Running a kernel module which uses d_path iteratively over the mnt_mountpoint members of the vfsmount structures which hang off of current->namespace->list, I get a curious doubling of the mount point names:
> 
> rootfs / rootfs
> /dev2/root2 / ext3
> proc /proc/proc proc
> sysfs /sys/sys sysfs
> devpts /dev/pts/dev/pts devpts
> tmpfs /dev/shm/dev/shm tmpfs
> /dev/hda1 /boot/boot ext2
> usbfs /proc/bus/usb/bus/usb usbfs
> 
> Is there any simple explanation? I have cross-checked and it appears _not_ be be an artifact of my programming, and I have no CLONE_NEWNS processes. Using the same algorithm with mnt_root produces correct results.  
> 
> The code follows:
> 
>         char *path;
> ...
>         namespace = current-> namespace
>         down_read(&namespace->sem);
>         list_for_each_entry(vfsmnt_ptr,&namespace->list,mnt_list) {
>                 mount = mntget(vfsmnt_ptr);
>                 dentry = dget(vfsmnt_ptr->mnt_mountpoint);

should be:

dentry = dget(vfsmnt_ptr->mnt_root);

> 
>                 device = vfsmnt_ptr->mnt_devname ? vfsmnt_ptr->mnt_devname : "none";
> 
>                 path = d_path(dentry, mount, buf, PAGE_SIZE);
>                 error = PTR_ERR(path);
>                 if(IS_ERR(path)) {
>                         dput(dentry);
>                         mntput(mount);
>                         goto out;
>                 }
> 
>                 fstype = vfsmnt_ptr->mnt_sb->s_type->name;
>                 printk("%s\t%s\t%s\n",device,path,fstype);
> ---
> 
> $ uname -a
> Linux nectarsys 2.6.10-1-k7 #1 Fri Mar 11 03:13:32 EST 2005 i686 GNU/Linux
> 
> 
> 
> 


Mike Waychison