Re: kern/39777: NFS client triggers kernel panics

[Matthias Scheler <tron%zhadum.org.uk@localhost>]

On Fri, Oct 31, 2008 at 06:30:11PM +0000, Matthias Scheler wrote:
> This looks like a stack overflow to me.

It seems that I'm right. The following change caused the problem:

http://mail-index.netbsd.org/source-changes/2008/10/17/msg211423.html

If I reduce the size of the stack arrays like this ...

Index: nfs_bio.c
===================================================================
RCS file: /cvsroot/src/sys/nfs/nfs_bio.c,v
retrieving revision 1.179
diff -u -r1.179 nfs_bio.c
--- nfs_bio.c   17 Oct 2008 14:24:43 -0000      1.179
+++ nfs_bio.c   31 Oct 2008 18:57:40 -0000
@@ -921,7 +921,7 @@
        int iomode;
        bool stalewriteverf = false;
        int i, npages = (bp->b_bcount + PAGE_SIZE - 1) >> PAGE_SHIFT;
-       struct vm_page **pgs, *spgs[64];
+       struct vm_page **pgs, *spgs[16];
 #ifndef NFS_V2_ONLY
        bool needcommit = true; /* need only COMMIT RPC */
 #else
@@ -1224,7 +1224,7 @@
        struct uvm_object *uobj = &vp->v_uobj;
        struct nfsnode *np = VTONFS(vp);
        const int npages = *ap->a_count;
-       struct vm_page *pg, **pgs, **opgs, *spgs[64];
+       struct vm_page *pg, **pgs, **opgs, *spgs[16];
        off_t origoffset, len;
        int i, error;
        bool v3 = NFS_ISV3(vp);

... the machine doesn't panic.

But that is probably not an appropriate fix. I wonder whether the stack
optimization should be eliminated.

        Kind regards

-- 
Matthias Scheler                                  http://zhadum.org.uk/