Re: [PATCH v1 20/23] NFS: Account for XDR pad of buf->pages

[Olga Kornievskaia <aglo@umich.edu>]

Hi Chuck,

This patch break ACLs. After applying this patch nfs4_getfacl fails
(it fails within xdr and returns ENOTSUPP). Any ideas why?

On Mon, Feb 11, 2019 at 11:25 AM Chuck Lever <chuck.lever@oracle.com> wrote:
>
> Certain NFS results (eg. READLINK) might expect a data payload that
> is not an exact multiple of 4 bytes. In this case, XDR encoding
> is required to pad that payload so its length on the wire is a
> multiple of 4 bytes. The constants that define the maximum size of
> each NFS result do not appear to account for this extra word.
>
> In each case where the data payload is to be received into pages:
>
> - 1 word is added to the size of the receive buffer allocated by
>   call_allocate
>
> - rpc_inline_rcv_pages subtracts 1 word from @hdrsize so that the
>   extra buffer space falls into the rcv_buf's tail iovec
>
> - If buf->pagelen is word-aligned, an XDR pad is not needed and
>   is thus removed from the tail
>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  fs/nfs/nfs2xdr.c  |    6 +++---
>  fs/nfs/nfs3xdr.c  |   10 +++++-----
>  fs/nfs/nfs4xdr.c  |   15 ++++++++-------
>  net/sunrpc/clnt.c |    6 +++++-
>  net/sunrpc/xdr.c  |    2 ++
>  5 files changed, 23 insertions(+), 16 deletions(-)
>
> diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
> index 1dcd0fe..a7ed29d 100644
> --- a/fs/nfs/nfs2xdr.c
> +++ b/fs/nfs/nfs2xdr.c
> @@ -56,11 +56,11 @@
>
>  #define NFS_attrstat_sz                (1+NFS_fattr_sz)
>  #define NFS_diropres_sz                (1+NFS_fhandle_sz+NFS_fattr_sz)
> -#define NFS_readlinkres_sz     (2)
> -#define NFS_readres_sz         (1+NFS_fattr_sz+1)
> +#define NFS_readlinkres_sz     (2+1)
> +#define NFS_readres_sz         (1+NFS_fattr_sz+1+1)
>  #define NFS_writeres_sz         (NFS_attrstat_sz)
>  #define NFS_stat_sz            (1)
> -#define NFS_readdirres_sz      (1)
> +#define NFS_readdirres_sz      (1+1)
>  #define NFS_statfsres_sz       (1+NFS_info_sz)
>
>  static int nfs_stat_to_errno(enum nfs_stat);
> diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
> index a54dcf4..110358f 100644
> --- a/fs/nfs/nfs3xdr.c
> +++ b/fs/nfs/nfs3xdr.c
> @@ -69,13 +69,13 @@
>  #define NFS3_removeres_sz      (NFS3_setattrres_sz)
>  #define NFS3_lookupres_sz      (1+NFS3_fh_sz+(2 * NFS3_post_op_attr_sz))
>  #define NFS3_accessres_sz      (1+NFS3_post_op_attr_sz+1)
> -#define NFS3_readlinkres_sz    (1+NFS3_post_op_attr_sz+1)
> -#define NFS3_readres_sz                (1+NFS3_post_op_attr_sz+3)
> +#define NFS3_readlinkres_sz    (1+NFS3_post_op_attr_sz+1+1)
> +#define NFS3_readres_sz                (1+NFS3_post_op_attr_sz+3+1)
>  #define NFS3_writeres_sz       (1+NFS3_wcc_data_sz+4)
>  #define NFS3_createres_sz      (1+NFS3_fh_sz+NFS3_post_op_attr_sz+NFS3_wcc_data_sz)
>  #define NFS3_renameres_sz      (1+(2 * NFS3_wcc_data_sz))
>  #define NFS3_linkres_sz                (1+NFS3_post_op_attr_sz+NFS3_wcc_data_sz)
> -#define NFS3_readdirres_sz     (1+NFS3_post_op_attr_sz+2)
> +#define NFS3_readdirres_sz     (1+NFS3_post_op_attr_sz+2+1)
>  #define NFS3_fsstatres_sz      (1+NFS3_post_op_attr_sz+13)
>  #define NFS3_fsinfores_sz      (1+NFS3_post_op_attr_sz+12)
>  #define NFS3_pathconfres_sz    (1+NFS3_post_op_attr_sz+6)
> @@ -85,7 +85,7 @@
>  #define ACL3_setaclargs_sz     (NFS3_fh_sz+1+ \
>                                 XDR_QUADLEN(NFS_ACL_INLINE_BUFSIZE))
>  #define ACL3_getaclres_sz      (1+NFS3_post_op_attr_sz+1+ \
> -                               XDR_QUADLEN(NFS_ACL_INLINE_BUFSIZE))
> +                               XDR_QUADLEN(NFS_ACL_INLINE_BUFSIZE)+1)
>  #define ACL3_setaclres_sz      (1+NFS3_post_op_attr_sz)
>
>  static int nfs3_stat_to_errno(enum nfs_stat);
> @@ -1629,7 +1629,7 @@ static int nfs3_xdr_dec_read3res(struct rpc_rqst *req, struct xdr_stream *xdr,
>         result->op_status = status;
>         if (status != NFS3_OK)
>                 goto out_status;
> -       result->replen = 3 + ((xdr_stream_pos(xdr) - pos) >> 2);
> +       result->replen = 4 + ((xdr_stream_pos(xdr) - pos) >> 2);
>         error = decode_read3resok(xdr, result);
>  out:
>         return error;
> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> index d0fa18d..6d9d5e2 100644
> --- a/fs/nfs/nfs4xdr.c
> +++ b/fs/nfs/nfs4xdr.c
> @@ -215,14 +215,14 @@ static int decode_layoutget(struct xdr_stream *xdr, struct rpc_rqst *req,
>                                  nfs4_fattr_bitmap_maxsz)
>  #define encode_read_maxsz      (op_encode_hdr_maxsz + \
>                                  encode_stateid_maxsz + 3)
> -#define decode_read_maxsz      (op_decode_hdr_maxsz + 2)
> +#define decode_read_maxsz      (op_decode_hdr_maxsz + 2 + 1)
>  #define encode_readdir_maxsz   (op_encode_hdr_maxsz + \
>                                  2 + encode_verifier_maxsz + 5 + \
>                                 nfs4_label_maxsz)
>  #define decode_readdir_maxsz   (op_decode_hdr_maxsz + \
> -                                decode_verifier_maxsz)
> +                                decode_verifier_maxsz + 1)
>  #define encode_readlink_maxsz  (op_encode_hdr_maxsz)
> -#define decode_readlink_maxsz  (op_decode_hdr_maxsz + 1)
> +#define decode_readlink_maxsz  (op_decode_hdr_maxsz + 1 + 1)
>  #define encode_write_maxsz     (op_encode_hdr_maxsz + \
>                                  encode_stateid_maxsz + 4)
>  #define decode_write_maxsz     (op_decode_hdr_maxsz + \
> @@ -284,14 +284,14 @@ static int decode_layoutget(struct xdr_stream *xdr, struct rpc_rqst *req,
>  #define decode_delegreturn_maxsz (op_decode_hdr_maxsz)
>  #define encode_getacl_maxsz    (encode_getattr_maxsz)
>  #define decode_getacl_maxsz    (op_decode_hdr_maxsz + \
> -                                nfs4_fattr_bitmap_maxsz + 1)
> +                                nfs4_fattr_bitmap_maxsz + 1 + 1)
>  #define encode_setacl_maxsz    (op_encode_hdr_maxsz + \
>                                  encode_stateid_maxsz + 3)
>  #define decode_setacl_maxsz    (decode_setattr_maxsz)
>  #define encode_fs_locations_maxsz \
>                                 (encode_getattr_maxsz)
>  #define decode_fs_locations_maxsz \
> -                               (0)
> +                               (1)
>  #define encode_secinfo_maxsz   (op_encode_hdr_maxsz + nfs4_name_maxsz)
>  #define decode_secinfo_maxsz   (op_decode_hdr_maxsz + 1 + ((NFS_MAX_SECFLAVORS * (16 + GSS_OID_MAX_LEN)) / 4))
>
> @@ -392,12 +392,13 @@ static int decode_layoutget(struct xdr_stream *xdr, struct rpc_rqst *req,
>                                 1 /* opaque devaddr4 length */ + \
>                                   /* devaddr4 payload is read into page */ \
>                                 1 /* notification bitmap length */ + \
> -                               1 /* notification bitmap, word 0 */)
> +                               1 /* notification bitmap, word 0 */ + \
> +                               1 /* possible XDR padding */)
>  #define encode_layoutget_maxsz (op_encode_hdr_maxsz + 10 + \
>                                 encode_stateid_maxsz)
>  #define decode_layoutget_maxsz (op_decode_hdr_maxsz + 8 + \
>                                 decode_stateid_maxsz + \
> -                               XDR_QUADLEN(PNFS_LAYOUT_MAXSIZE))
> +                               XDR_QUADLEN(PNFS_LAYOUT_MAXSIZE) + 1)
>  #define encode_layoutcommit_maxsz (op_encode_hdr_maxsz +          \
>                                 2 /* offset */ + \
>                                 2 /* length */ + \
> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> index f780605..4ea38b0 100644
> --- a/net/sunrpc/clnt.c
> +++ b/net/sunrpc/clnt.c
> @@ -1177,7 +1177,11 @@ void rpc_prepare_reply_pages(struct rpc_rqst *req, struct page **pages,
>                              unsigned int base, unsigned int len,
>                              unsigned int hdrsize)
>  {
> -       hdrsize += RPC_REPHDRSIZE + req->rq_cred->cr_auth->au_rslack;
> +       /* Subtract one to force an extra word of buffer space for the
> +        * payload's XDR pad to fall into the rcv_buf's tail iovec.
> +        */
> +       hdrsize += RPC_REPHDRSIZE + req->rq_cred->cr_auth->au_rslack - 1;
> +
>         xdr_inline_pages(&req->rq_rcv_buf, hdrsize << 2, pages, base, len);
>         trace_rpc_reply_pages(req);
>  }
> diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
> index 7cca515..aa8177d 100644
> --- a/net/sunrpc/xdr.c
> +++ b/net/sunrpc/xdr.c
> @@ -189,6 +189,8 @@ __be32 *xdr_encode_opaque(__be32 *p, const void *ptr, unsigned int nbytes)
>
>         tail->iov_base = buf + offset;
>         tail->iov_len = buflen - offset;
> +       if ((xdr->page_len & 3) == 0)
> +               tail->iov_len -= sizeof(__be32);
>
>         xdr->buflen += len;
>  }
>