NFSD: Optimize nfsd4_encode_fattr()

write_bytes_to_xdr_buf() is a generic way to place a variable-length
data item in an already-reserved spot in the encoding buffer.

However, it is costly. In nfsd4_encode_fattr(), it is unnecessary
because the data item is fixed in size and the buffer destination
address is always word-aligned.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index b52ea7d8313a11cd2a4c20ea52de85be31ce0015..e590236a60ab1f1508657ce55d44a66d00daa3e1 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2828,10 +2828,9 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
        struct kstat stat;
        struct svc_fh *tempfh = NULL;
        struct kstatfs statfs;
-       __be32 *p;
+       __be32 *p, *attrlen_p;
        int starting_len = xdr->buf->len;
        int attrlen_offset;
-       __be32 attrlen;
        u32 dummy;
        u64 dummy64;
        u32 rdattr_err = 0;
@@ -2919,10 +2918,9 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
                goto out;
 
        attrlen_offset = xdr->buf->len;
-       p = xdr_reserve_space(xdr, 4);
-       if (!p)
+       attrlen_p = xdr_reserve_space(xdr, XDR_UNIT);
+       if (!attrlen_p)
                goto out_resource;
-       p++;                /* to be backfilled later */
 
        if (bmval0 & FATTR4_WORD0_SUPPORTED_ATTRS) {
                u32 supp[3];
@@ -3344,8 +3342,7 @@ out_acl:
                *p++ = cpu_to_be32(err == 0);
        }
 
-       attrlen = htonl(xdr->buf->len - attrlen_offset - 4);
-       write_bytes_to_xdr_buf(xdr->buf, attrlen_offset, &attrlen, 4);
+       *attrlen_p = cpu_to_be32(xdr->buf->len - attrlen_offset - XDR_UNIT);
        status = nfs_ok;
 
 out: