Re: nfsdv4 leaks file descriptors

[Gerhard Heift <ml-nfs-linux-20110412-ef47@gheift.de>]

On Wed, Apr 13, 2011 at 05:12:11PM -0400, J. Bruce Fields wrote:
> On Tue, Apr 12, 2011 at 04:01:50PM +0200, Gerhard Heift wrote:
> > Hello,
> > 
> > I have a linux kernel (2.6.38.2, armv5tel) running which exports a
> > directory with following options:
> 
> Should be fixed in more recent stable kernel; let me know if not.

An even more recent stable than 2.6.38.2? I just compiled 2.6.39-rc3 and
there the leak happens too.

> --b.

Regards,
  Gerhard

> > /data ip/32(rw,async,crossmnt,insecure,root_squash,no_subtree_check,fsid=0)
> > 
> > On the client (Debian unstable, kernel 2.6.38-2-amd64) I mounted the
> > directory under /media(nfs4import with
> > 
> > # mount -t nfs4 ip:/ /media/nfs4import
> > 
> > After a lot running fdupes on this folder the server kernel starts
> > throwing messages like this one:
> > 
> >   VFS: file-max limit [number] reached
> > 
> > After a reboot I recognised that the number of used file descriptors
> > increases during the run of fdupes (see /proc/sys/fs/file-nr). Even
> > after unmounting the exported filesystem on the client, unexport the
> > file system on the server and stopping the nfs-server the file
> > descriptors are still allocated and unmounting the filesystem is not
> > possible.
> > 
> > After a little bit of research I could create a small program, which
> > increases the used file descriptors by one.
> > 
> > Regards,
> >   Gerhard
> 
> > #include <stdio.h>
> > 
> > #define DIR "/media/nfs4import/"
> > 
> > int main(void) {
> > 	FILE *f1;
> > 	FILE *f2;
> > 	char b[1024];
> > 	int i;
> > 
> > 	// create file1
> > 	f1 = fopen(DIR "file1.txt", "w");
> > 	fwrite("test\n", 5, 1, f1);
> > 	close(f1);
> > 
> > 	// open file1 in read mode
> > 	f1 = fopen(DIR "file1.txt", "r");
> > 
> > 	for (i = 0; i < 1; i++) {
> > 		// open file2 in write mode and close it
> > 		f2 = fopen(DIR "file2.txt", "w");
> > 		fclose(f2);
> > 	
> > 		// open file2 in read mode and close it
> > 		// this causes the leak of a file descriptor on the server
> > 		// just watch /proc/sys/fs/file-nr on the server
> > 		f2 = fopen(DIR "file2.txt", "r");
> > 		fclose(f2);
> > 	}
> > 	fclose(f1);
> > 
> > 	return 0;
> > }
> 
> 
>