java + procfs + nullfs = disaster

[Kostik Belousov]

On Thu, Aug 11, 2011 at 03:18:38PM -0400, b. f. wrote:
> I've run into a problem building java ports on my FreeBSD 9 amd64
> tinderbox.  Following an earlier suggestion,
> 
> http://www.marcuscom.com/pipermail/tinderbox-list/2010-September/001957.html
> 
> I've been performing builds in a tmpfs that is nullfs-mounted on a ufs
> mountpoint.  After building packages for java/diablo-jdk16 on
> {7.3,8.1}-{i386,amd64}, the ports that depend upon it fail when
> invoking java binary executables from that port, with:
> 
> Error: could not find libjava.so
> Error: could not find Java 2 Runtime Environment.
> 
> A search of the mailing lists reveals that this problem has occurred
> for the past several years, and has sometimes been attributed to the
> fact that a procfs is mounted on /proc, and sometimes to vague nullfs
> problems, but has never been solved:
> 
> http://lists.freebsd.org/pipermail/freebsd-java/2011-March/009169.html
> http://lists.freebsd.org/pipermail/freebsd-stable/2010-May/056814.html
> http://lists.freebsd.org/pipermail/freebsd-java/2009-May/008104.html
> http://lists.freebsd.org/pipermail/freebsd-java/2009-February/007854.html
> http://lists.freebsd.org/pipermail/freebsd-stable/2005-February/011629.html
> ...
> 
> However, it seems rather to be a combination of factors, because, for
> example, if I:
> 
> mount /proc
> mkdir /tmp/java
> tar -C /tmp/java -xvf
> /home/shared/freebsd/tinderbox/packages/8.1-amd64-u1/All/diablo-jdk-1.6.0.07.02_15.tbz
> cd /tmp/diablo-jdk1.6.0/bin
> truss ./java -version
> 
> , I obtain:
> 
> ...
> 
> readlink("/proc/curproc/file","/tmp/java/diablo-jdk1.6.0/bin/java",1024)
> = 35 (0x23)
> access("/tmp/java/diablo-jdk1.6.0/lib/amd64/libjava.so",0) ERR#2 'No
> such file or directory'
> access("/tmp/java/diablo-jdk1.6.0/jre/lib/amd64/libjava.so",0) = 0 (0x0)
> 
> ...
> 
> , and libjava.so is found.  Then, if I:
> 
>  umount /proc
> truss ./java -version
> 
> , the library is also found, in a slightly different manner:
> 
> +readlink("/proc/curproc/file",0x7fffffffca40,1024) ERR#2 'No such
> file or directory'
> +__getcwd("/tmp/java/diablo-jdk1.6.0/bin",1026)   = 0 (0x0)
> +stat("/tmp/java/diablo-jdk1.6.0/bin/./java",{ mode=-rwxr-xr-x
> ,inode=3121,size=95014,blksize=4096 }) = 0 (0x0)
> +lstat("/tmp",{ mode=drwxrwxrwt ,inode=2,size=600,blksize=4096 }) = 0 (0x0)
> +lstat("/tmp/java",{ mode=drwxr-xr-x ,inode=15,size=280,blksize=4096
> }) = 0 (0x0)
> +lstat("/tmp/java/diablo-jdk1.6.0",{ mode=drwxr-xr-x
> ,inode=3105,size=560,blksize=4096 }) = 0 (0x0)
> +lstat("/tmp/java/diablo-jdk1.6.0/bin",{ mode=drwxr-xr-x
> ,inode=3112,size=1720,blksize=4096 }) = 0 (0x0)
> +lstat("/tmp/java/diablo-jdk1.6.0/bin/java",{ mode=-rwxr-xr-x
> ,inode=3121,size=95014,blksize=4096 }) = 0 (0x0)
>  access("/tmp/java/diablo-jdk1.6.0/lib/amd64/libjava.so",0) ERR#2 'No
> such file or directory'
>  access("/tmp/java/diablo-jdk1.6.0/jre/lib/amd64/libjava.so",0) = 0 (0x0)
> 
> 
> However, if I:
> 
> rm -vr /tmp/java
> mount /proc
> mkdir /tmp/java /root/java
> mount -t nullfs /tmp/java /root/java
> tar -C /root/java -xvf
> /home/shared/freebsd/tinderbox/packages/8.1-amd64-u1/All/diablo-jdk-1.6.0.07.02_15.tbz
> cd /root/diablo-jdk1.6.0/bin
> truss ./java -version
> 
> then the library cannot be found:
> 
> readlink("/proc/curproc/file","unknown",1024)    = 7 (0x7)
> Error: could not find libjava.so
> write(2,"Error: could not find libjava.so"...,33) = 33 (0x21)
> Error: could not find Java 2 Runtime Environment.
> write(2,"Error: could not find Java 2 Run"...,50) = 50 (0x32)
This is a long-standing strangeness in our procfs. I wonder how much
will break after the following. Can you try ls -l /proc/<pid>/
in the situation when file previously shown 'unknown' ?

diff --git a/sys/fs/procfs/procfs.c b/sys/fs/procfs/procfs.c
index 8b69eb1..514e279 100644
--- a/sys/fs/procfs/procfs.c
+++ b/sys/fs/procfs/procfs.c
@@ -67,20 +67,23 @@
 int
 procfs_doprocfile(PFS_FILL_ARGS)
 {
-	char *fullpath = "unknown";
-	char *freepath = NULL;
+	char *fullpath;
+	char *freepath;
 	struct vnode *textvp;
+	int error;
 
+	freepath = NULL;
 	PROC_LOCK(p);
 	textvp = p->p_textvp;
 	vhold(textvp);
 	PROC_UNLOCK(p);
-	vn_fullpath(td, textvp, &fullpath, &freepath);
+	error = vn_fullpath(td, textvp, &fullpath, &freepath);
 	vdrop(textvp);
-	sbuf_printf(sb, "%s", fullpath);
-	if (freepath)
+	if (error == 0)
+		sbuf_printf(sb, "%s", fullpath);
+	if (freepath != NULL)
 		free(freepath, M_TEMP);
-	return (0);
+	return (error);
 }
 
 /*
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