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, 19 insertions, 17 deletions

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index c16b93df1bc1..3899ef3047f4 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -84,6 +84,7 @@ static int decode_layoutget(struct xdr_stream *xdr, struct rpc_rqst *req,
 /* lock,open owner id:
  * we currently use size 2 (u64) out of (NFS4_OPAQUE_LIMIT  >> 2)
  */
+#define pagepad_maxsz		(1)
 #define open_owner_id_maxsz	(1 + 2 + 1 + 1 + 2)
 #define lock_owner_id_maxsz	(1 + 1 + 4)
 #define decode_lockowner_maxsz	(1 + XDR_QUADLEN(IDMAP_NAMESZ))
@@ -215,14 +216,14 @@ 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 + 1)
+#define decode_read_maxsz	(op_decode_hdr_maxsz + 2 + pagepad_maxsz)
 #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 + 1)
+				 decode_verifier_maxsz + pagepad_maxsz)
 #define encode_readlink_maxsz	(op_encode_hdr_maxsz)
-#define decode_readlink_maxsz	(op_decode_hdr_maxsz + 1 + 1)
+#define decode_readlink_maxsz	(op_decode_hdr_maxsz + 1 + pagepad_maxsz)
 #define encode_write_maxsz	(op_encode_hdr_maxsz + \
 				 encode_stateid_maxsz + 4)
 #define decode_write_maxsz	(op_decode_hdr_maxsz + \
@@ -284,14 +285,14 @@ 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 + 1)
+				 nfs4_fattr_bitmap_maxsz + 1 + pagepad_maxsz)
 #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 \
-				(1)
+				(pagepad_maxsz)
 #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))
 
@@ -393,12 +394,13 @@ static int decode_layoutget(struct xdr_stream *xdr, struct rpc_rqst *req,
 				  /* devaddr4 payload is read into page */ \
 				1 /* notification bitmap length */ + \
 				1 /* notification bitmap, word 0 */ + \
-				1 /* possible XDR padding */)
+				pagepad_maxsz /* 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) + 1)
+				XDR_QUADLEN(PNFS_LAYOUT_MAXSIZE) + \
+				pagepad_maxsz)
 #define encode_layoutcommit_maxsz (op_encode_hdr_maxsz +          \
 				2 /* offset */ + \
 				2 /* length */ + \
@@ -2342,7 +2344,7 @@ static void nfs4_xdr_enc_open(struct rpc_rqst *req, struct xdr_stream *xdr,
 		encode_layoutget(xdr, args->lg_args, &hdr);
 		rpc_prepare_reply_pages(req, args->lg_args->layout.pages, 0,
 					args->lg_args->layout.pglen,
-					hdr.replen);
+					hdr.replen - pagepad_maxsz);
 	}
 	encode_nops(&hdr);
 }
@@ -2388,7 +2390,7 @@ static void nfs4_xdr_enc_open_noattr(struct rpc_rqst *req,
 		encode_layoutget(xdr, args->lg_args, &hdr);
 		rpc_prepare_reply_pages(req, args->lg_args->layout.pages, 0,
 					args->lg_args->layout.pglen,
-					hdr.replen);
+					hdr.replen - pagepad_maxsz);
 	}
 	encode_nops(&hdr);
 }
@@ -2499,7 +2501,7 @@ static void nfs4_xdr_enc_readlink(struct rpc_rqst *req, struct xdr_stream *xdr,
 	encode_readlink(xdr, args, req, &hdr);
 
 	rpc_prepare_reply_pages(req, args->pages, args->pgbase,
-				args->pglen, hdr.replen);
+				args->pglen, hdr.replen - pagepad_maxsz);
 	encode_nops(&hdr);
 }
 
@@ -2520,7 +2522,7 @@ static void nfs4_xdr_enc_readdir(struct rpc_rqst *req, struct xdr_stream *xdr,
 	encode_readdir(xdr, args, req, &hdr);
 
 	rpc_prepare_reply_pages(req, args->pages, args->pgbase,
-				args->count, hdr.replen);
+				args->count, hdr.replen - pagepad_maxsz);
 	encode_nops(&hdr);
 }
 
@@ -2541,7 +2543,7 @@ static void nfs4_xdr_enc_read(struct rpc_rqst *req, struct xdr_stream *xdr,
 	encode_read(xdr, args, &hdr);
 
 	rpc_prepare_reply_pages(req, args->pages, args->pgbase,
-				args->count, hdr.replen);
+				args->count, hdr.replen - pagepad_maxsz);
 	req->rq_rcv_buf.flags |= XDRBUF_READ;
 	encode_nops(&hdr);
 }
@@ -2588,7 +2590,7 @@ static void nfs4_xdr_enc_getacl(struct rpc_rqst *req, struct xdr_stream *xdr,
 			ARRAY_SIZE(nfs4_acl_bitmap), &hdr);
 
 	rpc_prepare_reply_pages(req, args->acl_pages, 0,
-				args->acl_len, replen + 1);
+				args->acl_len, replen);
 	encode_nops(&hdr);
 }
 
@@ -2810,7 +2812,7 @@ static void nfs4_xdr_enc_fs_locations(struct rpc_rqst *req,
 	}
 
 	rpc_prepare_reply_pages(req, (struct page **)&args->page, 0,
-				PAGE_SIZE, replen + 1);
+				PAGE_SIZE, replen);
 	encode_nops(&hdr);
 }
 
@@ -3014,14 +3016,14 @@ static void nfs4_xdr_enc_getdeviceinfo(struct rpc_rqst *req,
 	encode_compound_hdr(xdr, req, &hdr);
 	encode_sequence(xdr, &args->seq_args, &hdr);
 
-	replen = hdr.replen + op_decode_hdr_maxsz;
+	replen = hdr.replen + op_decode_hdr_maxsz + 2;
 
 	encode_getdeviceinfo(xdr, args, &hdr);
 
 	/* set up reply kvec. device_addr4 opaque data is read into the
 	 * pages */
 	rpc_prepare_reply_pages(req, args->pdev->pages, args->pdev->pgbase,
-				args->pdev->pglen, replen + 2 + 1);
+				args->pdev->pglen, replen);
 	encode_nops(&hdr);
 }
 
@@ -3043,7 +3045,7 @@ static void nfs4_xdr_enc_layoutget(struct rpc_rqst *req,
 	encode_layoutget(xdr, args, &hdr);
 
 	rpc_prepare_reply_pages(req, args->layout.pages, 0,
-				args->layout.pglen, hdr.replen);
+				args->layout.pglen, hdr.replen - pagepad_maxsz);
 	encode_nops(&hdr);
 }