Hi,
A kernel crash is observed on 3.1rc4 kernel when HIGHMEM is enabled and
kernel is booted with a NFS on omap4430sdp. The issue happens in the
below
scenario.
In file net/sunrpc/xprtsock.c,
static int xs_send_pagedata( xxx, struct xdr_buf *xdr, ..)
{
Struct page **ppage;
....
.....
ppage = xdr->pages + (base >> PAGE_SHIFT);
....
err = sock->ops->sendpage(sock, *ppage, base, len, flags);
...
}
1) In the above piece of code, the *ppage value from
ops->sendpage function is finally passed on to Kmap by the lower
level code to get the virtual address of the page.
2) In some corner cases the value of *ppage pointer is NULL.
3) When highmem is enabled and a NULL pointer is passed to
Kmap, then kmap finally crashes. But in the case when highmem
is disabled, then kmap returns a junk value for NULL pointer.
Highmem Enabled , kmap( NULL )-----> kernel crashes.
Highmem disabled, kmap( NULL )-----> junk value is
returned.
Subsequently this message
is observed on
the console.
"RPC call returned error 14"
4) Now the question is why is the value of *ppage = NULL is
passed
from the above piece of code to lower layers.
Should that not have handled *ppage = NULL? and kmap should not
have received a NULL pointer?
Thanks,
Sricharan