a issue about getting a devfs node's fullpath

[Zhichao1.Li at dell.com]

sorry my bad, your pitch works exactly, thank you so much


-----Original Message-----
From: Konstantin Belousov <kostikbel at gmail.com> 
Sent: Friday, October 11, 2019 4:29 PM
To: Li, Zhichao1 <Zhichao_Li1 at Dell.com>
Cc: freebsd-fs at freebsd.org; freebsd-drivers at freebsd.org; Hu, Shunchao <Shunchao_Hu at Dell.com>
Subject: Re: a issue about getting a devfs node's fullpath


[EXTERNAL EMAIL] 

On Fri, Oct 11, 2019 at 02:23:14AM +0000, Zhichao1.Li at dell.com wrote:
> Hello
> Thank you for your time
> Unfortunately it does not work, how about this way?
It does not work in which way ?  I tried it and it worked as expected.
Your patch is wrong, VOP_VPTOCNP() must return parent vnode, if any.

> 
> --- a/src/sys/fs/devfs/devfs_vnops.c
> +++ b/src/sys/fs/devfs/devfs_vnops.c
> @@ -293,7 +293,14 @@ devfs_vptocnp(struct vop_vptocnp_args *ap)
>                 }
>                 bcopy(dd->de_cdp->cdp_c.si_name, buf + i,
>                     strlen(dd->de_cdp->cdp_c.si_name));
> -               de = dd->de_dir;
> +               /*
> +                * when dealing with VCHR
> +                * the element 'si_name' already
> +                * holds the full path string
> +                * except rootdir, so just go
> +                * to the rootdir
> +                */
> +               de = dmp->dm_rootdir;
>         } else if (vp->v_type == VDIR) {
>                 if (dd == dmp->dm_rootdir) {
>                         *dvp = vp;
> @@ -307,13 +314,17 @@ devfs_vptocnp(struct vop_vptocnp_args *ap)
>                 }
>                 bcopy(dd->de_dirent->d_name, buf + i,
>                     dd->de_dirent->d_namlen);
> -               de = dd;
> +               /*
> +                * when dealing with VDIR
> +                * get its parent
> +                */
> +               de = devfs_parent_dirent(dd);
>         } else {
>                 error = ENOENT;
>                 goto finished;
>         }
>         *buflen = i;
> -       de = devfs_parent_dirent(de);
> +       /*no need to get another parent*/
>         if (de == NULL) {
>                 error = ENOENT;
>                 goto finished;
> 
> another thing is this func is called by many modules, I want to ensure modifying the func this way will not impact other modules and not bring some bugs, would you be so kind to help me out?
> 
> thank you
> 
> -----Original Message-----
> From: Konstantin Belousov <kib at freebsd.org>
> Sent: Thursday, October 10, 2019 11:40 PM
> To: Li, Zhichao1 <Zhichao_Li1 at Dell.com>
> Cc: freebsd-fs at freebsd.org; freebsd-drivers at freebsd.org; Hu, Shunchao 
> <Shunchao_Hu at Dell.com>
> Subject: Re: a issue about getting a devfs node's fullpath
> 
> 
> [EXTERNAL EMAIL]
> 
> On Thu, Oct 10, 2019 at 05:49:55AM +0000, Zhichao1.Li at dell.com wrote:
> > Dear freebsd developers
> > I know you're swamped, so I'll be brief.
> > I am trying to get a node's full under /dev by calling the function 'vn_fullpath', when dealing with things like '/dev/null' or '/dev/usb/1.0.1', it works well.
> > However when dealing a node under more than 2 sub directories (e.g. /dev/bus/usb/001/002)  which I made by calling 'make_dev_s' , it goes a little bit different, I got a string "/dev/bus/usb/bus/usb/001/002"
> > And I found the function 'devfs_vptocnp' gets the string wrongly 
> > when dealing multi slashes path string, I have remark the code as followed and put some comments would you please take a look, and tell me what the purpose this func pass the string that way?
> 
> Try this.  Not tested.
> 
> diff --git a/sys/fs/devfs/devfs_vnops.c b/sys/fs/devfs/devfs_vnops.c 
> index 3b80c68e309..f20b466d88b 100644
> --- a/sys/fs/devfs/devfs_vnops.c
> +++ b/sys/fs/devfs/devfs_vnops.c
> @@ -284,38 +284,27 @@ devfs_vptocnp(struct vop_vptocnp_args *ap)
>  	if (error != 0)
>  		return (error);
>  
> -	i = *buflen;
> +	if (vp->v_type != VCHR && vp->v_type != VDIR) {
> +		error = ENOENT;
> +		goto finished;
> +	}
> +
>  	dd = vp->v_data;
> +	if (vp->v_type == VDIR && dd == dmp->dm_rootdir) {
> +		*dvp = vp;
> +		vref(*dvp);
> +		goto finished;
> +	}
>  
> -	if (vp->v_type == VCHR) {
> -		i -= strlen(dd->de_cdp->cdp_c.si_name);
> -		if (i < 0) {
> -			error = ENOMEM;
> -			goto finished;
> -		}
> -		bcopy(dd->de_cdp->cdp_c.si_name, buf + i,
> -		    strlen(dd->de_cdp->cdp_c.si_name));
> -		de = dd->de_dir;
> -	} else if (vp->v_type == VDIR) {
> -		if (dd == dmp->dm_rootdir) {
> -			*dvp = vp;
> -			vref(*dvp);
> -			goto finished;
> -		}
> -		i -= dd->de_dirent->d_namlen;
> -		if (i < 0) {
> -			error = ENOMEM;
> -			goto finished;
> -		}
> -		bcopy(dd->de_dirent->d_name, buf + i,
> -		    dd->de_dirent->d_namlen);
> -		de = dd;
> -	} else {
> -		error = ENOENT;
> +	i = *buflen;
> +	i -= dd->de_dirent->d_namlen;
> +	if (i < 0) {
> +		error = ENOMEM;
>  		goto finished;
>  	}
> +	bcopy(dd->de_dirent->d_name, buf + i, dd->de_dirent->d_namlen);
>  	*buflen = i;
> -	de = devfs_parent_dirent(de);
> +	de = devfs_parent_dirent(dd);
>  	if (de == NULL) {
>  		error = ENOENT;
>  		goto finished;