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, 10 insertions, 9 deletions

diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index f6676af37d5d..7fba7711e6b3 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -34,6 +34,7 @@
  * Declare the space requirements for NFS arguments and replies as
  * number of 32bit-words
  */
+#define NFS_pagepad_sz		(1) /* Page padding */
 #define NFS_fhandle_sz		(8)
 #define NFS_sattr_sz		(8)
 #define NFS_filename_sz		(1+(NFS2_MAXNAMLEN>>2))
@@ -56,11 +57,11 @@
 
 #define NFS_attrstat_sz		(1+NFS_fattr_sz)
 #define NFS_diropres_sz		(1+NFS_fhandle_sz+NFS_fattr_sz)
-#define NFS_readlinkres_sz	(2+1)
-#define NFS_readres_sz		(1+NFS_fattr_sz+1+1)
+#define NFS_readlinkres_sz	(2+NFS_pagepad_sz)
+#define NFS_readres_sz		(1+NFS_fattr_sz+1+NFS_pagepad_sz)
 #define NFS_writeres_sz         (NFS_attrstat_sz)
 #define NFS_stat_sz		(1)
-#define NFS_readdirres_sz	(1+1)
+#define NFS_readdirres_sz	(1+NFS_pagepad_sz)
 #define NFS_statfsres_sz	(1+NFS_info_sz)
 
 static int nfs_stat_to_errno(enum nfs_stat);
@@ -592,8 +593,8 @@ static void nfs2_xdr_enc_readlinkargs(struct rpc_rqst *req,
 	const struct nfs_readlinkargs *args = data;
 
 	encode_fhandle(xdr, args->fh);
-	rpc_prepare_reply_pages(req, args->pages, args->pgbase,
-				args->pglen, NFS_readlinkres_sz);
+	rpc_prepare_reply_pages(req, args->pages, args->pgbase, args->pglen,
+				NFS_readlinkres_sz - NFS_pagepad_sz);
 }
 
 /*
@@ -628,8 +629,8 @@ static void nfs2_xdr_enc_readargs(struct rpc_rqst *req,
 	const struct nfs_pgio_args *args = data;
 
 	encode_readargs(xdr, args);
-	rpc_prepare_reply_pages(req, args->pages, args->pgbase,
-				args->count, NFS_readres_sz);
+	rpc_prepare_reply_pages(req, args->pages, args->pgbase, args->count,
+				NFS_readres_sz - NFS_pagepad_sz);
 	req->rq_rcv_buf.flags |= XDRBUF_READ;
 }
 
@@ -786,8 +787,8 @@ static void nfs2_xdr_enc_readdirargs(struct rpc_rqst *req,
 	const struct nfs_readdirargs *args = data;
 
 	encode_readdirargs(xdr, args);
-	rpc_prepare_reply_pages(req, args->pages, 0,
-				args->count, NFS_readdirres_sz);
+	rpc_prepare_reply_pages(req, args->pages, 0, args->count,
+				NFS_readdirres_sz - NFS_pagepad_sz);
 }
 
 /*