NFS: Request fh_expire_type attribute in "server caps" operation

The fh_expire_type file attribute is a filesystem wide attribute that
consists of flags that indicate what characteristics file handles
on this FSID have.

Our client doesn't support volatile file handles.  It should find
out early (say, at mount time) whether the server is going to play
shenanighans with file handles during a migration.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index a6fb55da874c..3e0fe9f92e7c 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -2676,6 +2676,7 @@ static void nfs4_xdr_enc_server_caps(struct rpc_rqst *req,
         encode_sequence(xdr, &args->seq_args, &hdr);
         encode_putfh(xdr, args->fhandle, &hdr);
         encode_getattr_one(xdr, FATTR4_WORD0_SUPPORTED_ATTRS|
+                           FATTR4_WORD0_FH_EXPIRE_TYPE|
                            FATTR4_WORD0_LINK_SUPPORT|
                            FATTR4_WORD0_SYMLINK_SUPPORT|
                            FATTR4_WORD0_ACLSUPPORT, &hdr);
@@ -3223,6 +3224,28 @@ out_overflow:
         return -EIO;
 }
 
+static int decode_attr_fh_expire_type(struct xdr_stream *xdr,
+                                      uint32_t *bitmap, uint32_t *type)
+{
+        __be32 *p;
+
+        *type = 0;
+        if (unlikely(bitmap[0] & (FATTR4_WORD0_FH_EXPIRE_TYPE - 1U)))
+                return -EIO;
+        if (likely(bitmap[0] & FATTR4_WORD0_FH_EXPIRE_TYPE)) {
+                p = xdr_inline_decode(xdr, 4);
+                if (unlikely(!p))
+                        goto out_overflow;
+                *type = be32_to_cpup(p);
+                bitmap[0] &= ~FATTR4_WORD0_FH_EXPIRE_TYPE;
+        }
+        dprintk("%s: expire type=0x%x\n", __func__, *type);
+        return 0;
+out_overflow:
+        print_overflow_msg(__func__, xdr);
+        return -EIO;
+}
+
 static int decode_attr_change(struct xdr_stream *xdr, uint32_t *bitmap, uint64_t *change)
 {
         __be32 *p;
@@ -4271,6 +4294,9 @@ static int decode_server_caps(struct xdr_stream *xdr, struct nfs4_server_caps_re
                 goto xdr_error;
         if ((status = decode_attr_supported(xdr, bitmap, res->attr_bitmask)) != 0)
                 goto xdr_error;
+        if ((status = decode_attr_fh_expire_type(xdr, bitmap,
+                                                 &res->fh_expire_type)) != 0)
+                goto xdr_error;
         if ((status = decode_attr_link_support(xdr, bitmap, &res->has_links)) != 0)
                 goto xdr_error;
         if ((status = decode_attr_symlink_support(xdr, bitmap, &res->has_symlinks)) != 0)