[PATCH] knfsd: nfsd4: fix corruption of returned data when using 64k pages

In v4 we grab an extra page just for the padding of returned data.  The
formula that the rpc server uses to allocate pages for the response doesn't
take into account this extra page.

Instead of adjusting those formulae, we adopt the same solution as v2 and v3,
and put the "tail" data in the same page as the "head" data.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 845f25251d817fb14055cd6ea7ce782c55f0ac83..f2710cfc0bc586e73dc3fd735e77fdbfc15a8c6c 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2084,27 +2084,20 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_read
        WRITE32(eof);
        WRITE32(maxcount);
        ADJUST_ARGS();
-       resp->xbuf->head[0].iov_len = ((char*)resp->p) - (char*)resp->xbuf->head[0].iov_base;
-
+       resp->xbuf->head[0].iov_len = (char*)p
+                                       - (char*)resp->xbuf->head[0].iov_base;
        resp->xbuf->page_len = maxcount;
 
-       /* read zero bytes -> don't set up tail */
-       if(!maxcount)
-               return 0;        
-
-       /* set up page for remaining responses */
-       svc_take_page(resp->rqstp);
-       resp->xbuf->tail[0].iov_base = 
-               page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);
-       resp->rqstp->rq_restailpage = resp->rqstp->rq_resused-1;
+       /* Use rest of head for padding and remaining ops: */
+       resp->rqstp->rq_restailpage = 0;
+       resp->xbuf->tail[0].iov_base = p;
        resp->xbuf->tail[0].iov_len = 0;
-       resp->p = resp->xbuf->tail[0].iov_base;
-       resp->end = resp->p + PAGE_SIZE/4;
-
        if (maxcount&3) {
-               *(resp->p)++ = 0;
+               RESERVE_SPACE(4);
+               WRITE32(0);
                resp->xbuf->tail[0].iov_base += maxcount&3;
                resp->xbuf->tail[0].iov_len = 4 - (maxcount&3);
+               ADJUST_ARGS();
        }
        return 0;
 }
@@ -2141,21 +2134,20 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_r
 
        WRITE32(maxcount);
        ADJUST_ARGS();
-       resp->xbuf->head[0].iov_len = ((char*)resp->p) - (char*)resp->xbuf->head[0].iov_base;
+       resp->xbuf->head[0].iov_len = (char*)p
+                               - (char*)resp->xbuf->head[0].iov_base;
+       resp->xbuf->page_len = maxcount;
 
-       svc_take_page(resp->rqstp);
-       resp->xbuf->tail[0].iov_base = 
-               page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);
-       resp->rqstp->rq_restailpage = resp->rqstp->rq_resused-1;
+       /* Use rest of head for padding and remaining ops: */
+       resp->rqstp->rq_restailpage = 0;
+       resp->xbuf->tail[0].iov_base = p;
        resp->xbuf->tail[0].iov_len = 0;
-       resp->p = resp->xbuf->tail[0].iov_base;
-       resp->end = resp->p + PAGE_SIZE/4;
-
-       resp->xbuf->page_len = maxcount;
        if (maxcount&3) {
-               *(resp->p)++ = 0;
+               RESERVE_SPACE(4);
+               WRITE32(0);
                resp->xbuf->tail[0].iov_base += maxcount&3;
                resp->xbuf->tail[0].iov_len = 4 - (maxcount&3);
+               ADJUST_ARGS();
        }
        return 0;
 }