mbuf size and NFS

[Martin Karsten]

Some time ago I wanted to do experiments with a reduced mbuf size, just 
for the sake of it. Changing MSIZE (to 128 in this case) and recompiling 
the kernel seemed to do the job, although I only tested fairly standard 
functionality. This was on a 5.4-RELEASE system.

However, I noticed one problem with NFS which seems to be easily 
fixable. The following patch is for
src/sys/nfs/nfs_common.c,v 1.117.2.1 2005/10/09

@@ -187,7 +187,9 @@
         } else if (mp->m_next == NULL) {
                 return NULL;
         } else if (siz > MHLEN) {
-               panic("nfs S too big");
+               MCLGET(mp2, how);
+               if (mp2 == NULL)
+                       return NULL;
         } else {
                 MGET(mp2, how, MT_DATA);
                 if (mp2 == NULL)

I actually tested it with 'how' being hardcoded to M_TRYWAIT.

I just wanted to flag this to see whether the fix is obviously wrong or 
whether a such change could be incorporated into the kernel.

Thanks,
Martin