SUNRPC: Clean up the handling of page padding in rpc_prepare_reply_pages()

rpc_prepare_reply_pages() currently expects the 'hdrsize' argument to
contain the length of the data that we expect to want placed in the head
kvec plus a count of 1 word of padding that is placed after the page data.
This is very confusing when trying to read the code, and sometimes leads
to callers adding an arbitrary value of '1' just in order to satisfy the
requirement (whether or not the page data actually needs such padding).

This patch aims to clarify the code by changing the 'hdrsize' argument
to remove that 1 word of padding. This means we need to subtract the
padding from all the existing callers.

Fixes: 02ef04e432ba ("NFS: Account for XDR pad of buf->pages")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

1 files changed, 16 insertions, 13 deletions

diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index 69971f6c840d..ca10072644ff 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -33,6 +33,7 @@
  * Declare the space requirements for NFS arguments and replies as
  * number of 32bit-words
  */
+#define NFS3_pagepad_sz		(1) /* Page padding */
 #define NFS3_fhandle_sz		(1+16)
 #define NFS3_fh_sz		(NFS3_fhandle_sz)	/* shorthand */
 #define NFS3_sattr_sz		(15)
@@ -69,13 +70,13 @@
 #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+1)
-#define NFS3_readres_sz		(1+NFS3_post_op_attr_sz+3+1)
+#define NFS3_readlinkres_sz	(1+NFS3_post_op_attr_sz+1+NFS3_pagepad_sz)
+#define NFS3_readres_sz		(1+NFS3_post_op_attr_sz+3+NFS3_pagepad_sz)
 #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+1)
+#define NFS3_readdirres_sz	(1+NFS3_post_op_attr_sz+2+NFS3_pagepad_sz)
 #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 +86,8 @@
 #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)+1)
+				XDR_QUADLEN(NFS_ACL_INLINE_BUFSIZE)+\
+				NFS3_pagepad_sz)
 #define ACL3_setaclres_sz	(1+NFS3_post_op_attr_sz)
 
 static int nfs3_stat_to_errno(enum nfs_stat);
@@ -909,8 +911,8 @@ static void nfs3_xdr_enc_readlink3args(struct rpc_rqst *req,
 	const struct nfs3_readlinkargs *args = data;
 
 	encode_nfs_fh3(xdr, args->fh);
-	rpc_prepare_reply_pages(req, args->pages, args->pgbase,
-				args->pglen, NFS3_readlinkres_sz);
+	rpc_prepare_reply_pages(req, args->pages, args->pgbase, args->pglen,
+				NFS3_readlinkres_sz - NFS3_pagepad_sz);
 }
 
 /*
@@ -939,7 +941,8 @@ static void nfs3_xdr_enc_read3args(struct rpc_rqst *req,
 				   const void *data)
 {
 	const struct nfs_pgio_args *args = data;
-	unsigned int replen = args->replen ? args->replen : NFS3_readres_sz;
+	unsigned int replen = args->replen ? args->replen :
+					     NFS3_readres_sz - NFS3_pagepad_sz;
 
 	encode_read3args(xdr, args);
 	rpc_prepare_reply_pages(req, args->pages, args->pgbase,
@@ -1239,8 +1242,8 @@ static void nfs3_xdr_enc_readdir3args(struct rpc_rqst *req,
 	const struct nfs3_readdirargs *args = data;
 
 	encode_readdir3args(xdr, args);
-	rpc_prepare_reply_pages(req, args->pages, 0,
-				args->count, NFS3_readdirres_sz);
+	rpc_prepare_reply_pages(req, args->pages, 0, args->count,
+				NFS3_readdirres_sz - NFS3_pagepad_sz);
 }
 
 /*
@@ -1281,8 +1284,8 @@ static void nfs3_xdr_enc_readdirplus3args(struct rpc_rqst *req,
 	const struct nfs3_readdirargs *args = data;
 
 	encode_readdirplus3args(xdr, args);
-	rpc_prepare_reply_pages(req, args->pages, 0,
-				args->count, NFS3_readdirres_sz);
+	rpc_prepare_reply_pages(req, args->pages, 0, args->count,
+				NFS3_readdirres_sz - NFS3_pagepad_sz);
 }
 
 /*
@@ -1328,7 +1331,7 @@ static void nfs3_xdr_enc_getacl3args(struct rpc_rqst *req,
 	if (args->mask & (NFS_ACL | NFS_DFACL)) {
 		rpc_prepare_reply_pages(req, args->pages, 0,
 					NFSACL_MAXPAGES << PAGE_SHIFT,
-					ACL3_getaclres_sz);
+					ACL3_getaclres_sz - NFS3_pagepad_sz);
 		req->rq_rcv_buf.flags |= XDRBUF_SPARSE_PAGES;
 	}
 }
@@ -1648,7 +1651,7 @@ 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 = 4 + ((xdr_stream_pos(xdr) - pos) >> 2);
+	result->replen = 3 + ((xdr_stream_pos(xdr) - pos) >> 2);
 	error = decode_read3resok(xdr, result);
 out:
 	return error;