Bernd Walter wrote:

On Thu, Nov 13, 2003 at 12:54:18AM -0800, Kris Kennaway wrote:


On Thu, Nov 13, 2003 at 06:44:25PM +1100, Peter Jeremy wrote:


On Wed, Nov 12, 2003 at 06:04:00PM -0800, Kris Kennaway wrote:


...my sparc machine reports that my i386 nfs server has 15 exabytes of
free space!

enigma# df -k
Filesystem 1K-blocks Used Avail Capacity Mounted on
rot13:/mnt2 56595176 54032286 18014398507517260 0% /rot13/mnt2


18014398507517260 = 2^54 - 1964724. and 2^54KB == 2^64 bytes. Is it
possible that rot13:/mnt2 has negative free space? (ie it's into the
8-10% reserved area).


Yes, that's precisely what it is..the bug is either in df or the
kernel (I suspect the latter, i.e. something in the nfs code).



And it's nothing new - I'm seeing this since several years now.



The NFS protocols have unsigned fields where statfs has signed equivalents: NFS can't represent negative available disk space ( Without the knowledge of the underlying filesystem on the server, negative free space is a little nonsensical anyway, I suppose)


The attached patch stops the NFS server assigning negative values to unsigned fields in the statfs response, and works against my local solaris box. Seem reasonable?
Index: nfs_serv.c
===================================================================
RCS file: /pub/FreeBSD/development/FreeBSD-CVS/src/sys/nfsserver/nfs_serv.c,v
retrieving revision 1.137
diff -u -r1.137 nfs_serv.c
--- nfs_serv.c  24 Oct 2003 18:36:49 -0000      1.137
+++ nfs_serv.c  14 Nov 2003 13:27:42 -0000
@@ -3812,7 +3812,7 @@
                tval = (u_quad_t)sf->f_bfree;
                tval *= (u_quad_t)sf->f_bsize;
                txdr_hyper(tval, &sfp->sf_fbytes);
-               tval = (u_quad_t)sf->f_bavail;
+               tval = sf->f_bavail > 0 ? (u_quad_t)sf->f_bavail : 0;
                tval *= (u_quad_t)sf->f_bsize;
                txdr_hyper(tval, &sfp->sf_abytes);
                sfp->sf_tfiles.nfsuquad[0] = 0;
@@ -3827,7 +3827,8 @@
                sfp->sf_bsize = txdr_unsigned(sf->f_bsize);
                sfp->sf_blocks = txdr_unsigned(sf->f_blocks);
                sfp->sf_bfree = txdr_unsigned(sf->f_bfree);
-               sfp->sf_bavail = txdr_unsigned(sf->f_bavail);
+               sfp->sf_bavail = txdr_unsigned(sf->f_bavail > 0 ?
+                   sf->f_bavail : 0);
        }
 nfsmout:
        if (vp)
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