nfsd4: don't treat readlink like a zero-copy operation

There's no advantage to this zero-copy-style readlink encoding, and it
unnecessarily limits the kinds of compounds we can handle.  (In practice
I can't see why a client would want e.g. multiple readlink calls in a
comound, but it's probably a spec violation for us not to handle it.)

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 12 insertions, 30 deletions

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 3f2a52ccb9d1..cda6226bda91 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3160,8 +3160,9 @@ static __be32
 nfsd4_encode_readlink(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_readlink *readlink)
 {
         int maxcount;
+        __be32 wire_count;
+        int zero = 0;
         struct xdr_stream *xdr = &resp->xdr;
-        char *page;
         int length_offset = xdr->buf->len;
         __be32 *p;
 
@@ -3171,26 +3172,19 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd
         p = xdr_reserve_space(xdr, 4);
         if (!p)
                 return nfserr_resource;
-
-        if (resp->xdr.buf->page_len)
-                return nfserr_resource;
-        if (!*resp->rqstp->rq_next_page)
-                return nfserr_resource;
-
-        page = page_address(*(resp->rqstp->rq_next_page++));
-
         maxcount = PAGE_SIZE;
 
-        if (xdr->end - xdr->p < 1)
+        p = xdr_reserve_space(xdr, maxcount);
+        if (!p)
                 return nfserr_resource;
-
         /*
          * XXX: By default, the ->readlink() VFS op will truncate symlinks
          * if they would overflow the buffer.  Is this kosher in NFSv4?  If
          * not, one easy fix is: if ->readlink() precisely fills the buffer,
          * assume that truncation occurred, and return NFS4ERR_RESOURCE.
          */
-        nfserr = nfsd_readlink(readlink->rl_rqstp, readlink->rl_fhp, page, &maxcount);
+        nfserr = nfsd_readlink(readlink->rl_rqstp, readlink->rl_fhp,
+                                                (char *)p, &maxcount);
         if (nfserr == nfserr_isdir)
                 nfserr = nfserr_inval;
         if (nfserr) {
@@ -3198,24 +3192,12 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd
                 return nfserr;
         }
 
-        WRITE32(maxcount);
-        resp->xdr.buf->head[0].iov_len = (char *)p
-                                - (char *)resp->xdr.buf->head[0].iov_base;
-        resp->xdr.buf->page_len = maxcount;
-        xdr->buf->len += maxcount;
-        xdr->page_ptr += 1;
-        xdr->buf->buflen -= PAGE_SIZE;
-        xdr->iov = xdr->buf->tail;
-
-        /* Use rest of head for padding and remaining ops: */
-        resp->xdr.buf->tail[0].iov_base = p;
-        resp->xdr.buf->tail[0].iov_len = 0;
-        if (maxcount&3) {
-                p = xdr_reserve_space(xdr, 4);
-                WRITE32(0);
-                resp->xdr.buf->tail[0].iov_base += maxcount&3;
-                resp->xdr.buf->tail[0].iov_len = 4 - (maxcount&3);
-        }
+        wire_count = htonl(maxcount);
+        write_bytes_to_xdr_buf(xdr->buf, length_offset, &wire_count, 4);
+        xdr_truncate_encode(xdr, length_offset + 4 + maxcount);
+        if (maxcount & 3)
+                write_bytes_to_xdr_buf(xdr->buf, length_offset + 4 + maxcount,
+                                                &zero, 4 - (maxcount&3));
         return 0;
 }