[PATCH 13/13] NFS: Request fh_expire_type attribute in "server caps" operation

[Chuck Lever <chuck.lever@oracle.com>]

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 won't support volatile file handles, but it should find
out 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>
---

 fs/nfs/nfs4proc.c         |    1 +
 fs/nfs/nfs4xdr.c          |   26 ++++++++++++++++++++++++++
 include/linux/nfs_fs_sb.h |    3 +++
 include/linux/nfs_xdr.h   |    1 +
 4 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index aa0d2cd..037d4ca 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2181,6 +2181,7 @@ static int _nfs4_server_capabilities(struct nfs_server *server, struct nfs_fh *f
 		server->cache_consistency_bitmask[0] &= FATTR4_WORD0_CHANGE|FATTR4_WORD0_SIZE;
 		server->cache_consistency_bitmask[1] &= FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY;
 		server->acl_bitmask = res.acl_bitmask;
+		server->fh_expire_type = res.fh_expire_type;
 	}
 
 	return status;
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 6b1052a..25e82a6 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -2634,6 +2634,7 @@ 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);
@@ -3181,6 +3182,28 @@ 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;
@@ -4209,6 +4232,9 @@ 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)
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 6532d7b..f07d966 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -144,6 +144,9 @@ struct nfs_server {
 	u32			acl_bitmask;	/* V4 bitmask representing the ACEs
 						   that are supported on this
 						   filesystem */
+	u32			fh_expire_type;	/* V4 bitmask representing file
+						   handle volatility type for
+						   this filesystem */
 	struct pnfs_layoutdriver_type  *pnfs_curr_ld; /* Active layout driver */
 	struct rpc_wait_queue	roc_rpcwaitq;
 	void			*pnfs_ld_data;	/* per mount point data */
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index d609631..ff74d94 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -973,6 +973,7 @@ struct nfs4_server_caps_res {
 	u32				acl_bitmask;
 	u32				has_links;
 	u32				has_symlinks;
+	u32				fh_expire_type;
 	struct nfs4_sequence_res	seq_res;
 };