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Date:      Fri, 11 Oct 2019 02:23:14 +0000
From:      <Zhichao1.Li@dell.com>
To:        <kib@freebsd.org>
Cc:        <freebsd-fs@freebsd.org>, <freebsd-drivers@freebsd.org>, <Shunchao.Hu@dell.com>
Subject:   RE: a issue about getting a devfs node's fullpath
Message-ID:  <54b7173c96df43689de04f848ca86de6@KULX13MDC103.APAC.DELL.COM>
In-Reply-To: <20191010153932.GO44691@kib.kiev.ua>
References:  <c6d34bd0b4114bee956b0af6d680a67f@KULX13MDC103.APAC.DELL.COM> <20191010153932.GO44691@kib.kiev.ua>

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Hello
Thank you for your time
Unfortunately it does not work, how about this way?

--- 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 =3D 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 =3D dmp->dm_rootdir;
        } else if (vp->v_type =3D=3D VDIR) {
                if (dd =3D=3D dmp->dm_rootdir) {
                        *dvp =3D 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 =3D dd;
+               /*
+                * when dealing with VDIR
+                * get its parent
+                */
+               de =3D devfs_parent_dirent(dd);
        } else {
                error =3D ENOENT;
                goto finished;
        }
        *buflen =3D i;
-       de =3D devfs_parent_dirent(de);
+       /*no need to get another parent*/
        if (de =3D=3D NULL) {
                error =3D ENOENT;
                goto finished;

another thing is this func is called by many modules, I want to ensure modi=
fying the func this way will not impact other modules and not bring some bu=
gs, would you be so kind to help me out?

thank you=20

-----Original Message-----
From: Konstantin Belousov <kib@freebsd.org>=20
Sent: Thursday, October 10, 2019 11:40 PM
To: Li, Zhichao1 <Zhichao_Li1@Dell.com>
Cc: freebsd-fs@freebsd.org; freebsd-drivers@freebsd.org; Hu, Shunchao <Shun=
chao_Hu@Dell.com>
Subject: Re: a issue about getting a devfs node's fullpath


[EXTERNAL EMAIL]=20

On Thu, Oct 10, 2019 at 05:49:55AM +0000, Zhichao1.Li@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_f=
ullpath', 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 b=
it different, I got a string "/dev/bus/usb/bus/usb/001/002"
> And I found the function 'devfs_vptocnp' gets the string wrongly when=20
> 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 purpo=
se 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 !=3D 0)
 		return (error);
=20
-	i =3D *buflen;
+	if (vp->v_type !=3D VCHR && vp->v_type !=3D VDIR) {
+		error =3D ENOENT;
+		goto finished;
+	}
+
 	dd =3D vp->v_data;
+	if (vp->v_type =3D=3D VDIR && dd =3D=3D dmp->dm_rootdir) {
+		*dvp =3D vp;
+		vref(*dvp);
+		goto finished;
+	}
=20
-	if (vp->v_type =3D=3D VCHR) {
-		i -=3D strlen(dd->de_cdp->cdp_c.si_name);
-		if (i < 0) {
-			error =3D ENOMEM;
-			goto finished;
-		}
-		bcopy(dd->de_cdp->cdp_c.si_name, buf + i,
-		    strlen(dd->de_cdp->cdp_c.si_name));
-		de =3D dd->de_dir;
-	} else if (vp->v_type =3D=3D VDIR) {
-		if (dd =3D=3D dmp->dm_rootdir) {
-			*dvp =3D vp;
-			vref(*dvp);
-			goto finished;
-		}
-		i -=3D dd->de_dirent->d_namlen;
-		if (i < 0) {
-			error =3D ENOMEM;
-			goto finished;
-		}
-		bcopy(dd->de_dirent->d_name, buf + i,
-		    dd->de_dirent->d_namlen);
-		de =3D dd;
-	} else {
-		error =3D ENOENT;
+	i =3D *buflen;
+	i -=3D dd->de_dirent->d_namlen;
+	if (i < 0) {
+		error =3D ENOMEM;
 		goto finished;
 	}
+	bcopy(dd->de_dirent->d_name, buf + i, dd->de_dirent->d_namlen);
 	*buflen =3D i;
-	de =3D devfs_parent_dirent(de);
+	de =3D devfs_parent_dirent(dd);
 	if (de =3D=3D NULL) {
 		error =3D ENOENT;
 		goto finished;



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