[PATCH 1/2] NFSv3: Improve NFSv3 performance when server returns no post-op attributes

[PATCH 1/2] NFSv3: Improve NFSv3 performance when server returns no post-op attributes

[Trond Myklebust]

From: Trond Myklebust <trond.myklebust@primarydata.com>

When the server fails to return post-op attributes, the client's
attempt to place read data directly in the page cache fails, and
so we have to do an extra copy in order to realign the data with
page borders.
This patch attempts to detect servers that don't return post-op
attributes on read (e.g. for pNFS) and adjusts the placement
calculation accordingly.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/nfs3proc.c         | 5 +++++
 fs/nfs/nfs3xdr.c          | 7 ++++++-
 include/linux/nfs_fs_sb.h | 3 +++
 include/linux/nfs_xdr.h   | 3 ++-
 4 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c
index ec8a9efa268f..71bc16225b98 100644
--- a/fs/nfs/nfs3proc.c
+++ b/fs/nfs/nfs3proc.c
@@ -786,6 +786,7 @@ nfs3_proc_pathconf(struct nfs_server *server, struct nfs_fh *fhandle,
 static int nfs3_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 {
 	struct inode *inode = hdr->inode;
+	struct nfs_server *server = NFS_SERVER(inode);
 
 	if (hdr->pgio_done_cb != NULL)
 		return hdr->pgio_done_cb(task, hdr);
@@ -793,6 +794,9 @@ static int nfs3_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 	if (nfs3_async_handle_jukebox(task, inode))
 		return -EAGAIN;
 
+	if (task->tk_status >= 0 && !server->read_hdrsize)
+		cmpxchg(&server->read_hdrsize, 0, hdr->res.replen);
+
 	nfs_invalidate_atime(inode);
 	nfs_refresh_inode(inode, &hdr->fattr);
 	return 0;
@@ -802,6 +806,7 @@ static void nfs3_proc_read_setup(struct nfs_pgio_header *hdr,
 				 struct rpc_message *msg)
 {
 	msg->rpc_proc = &nfs3_procedures[NFS3PROC_READ];
+	hdr->args.replen = NFS_SERVER(hdr->inode)->read_hdrsize;
 }
 
 static int nfs3_proc_pgio_rpc_prepare(struct rpc_task *task,
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index d8c4c10b15f7..91ae2667f9e4 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -983,10 +983,11 @@ 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;
 
 	encode_read3args(xdr, args);
 	prepare_reply_buffer(req, args->pages, args->pgbase,
-					args->count, NFS3_readres_sz);
+					args->count, replen);
 	req->rq_rcv_buf.flags |= XDRBUF_READ;
 }
 
@@ -1675,9 +1676,12 @@ static int nfs3_xdr_dec_read3res(struct rpc_rqst *req, struct xdr_stream *xdr,
 				 void *data)
 {
 	struct nfs_pgio_res *result = data;
+	struct nfs_server *server = result->server;
+	unsigned int replen, pos;
 	enum nfs_stat status;
 	int error;
 
+	pos = xdr_stream_pos(xdr);
 	error = decode_nfsstat3(xdr, &status);
 	if (unlikely(error))
 		goto out;
@@ -1687,6 +1691,7 @@ 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 = 3 + ((xdr_stream_pos(xdr) - pos) >> 2);
 	error = decode_read3resok(xdr, result);
 out:
 	return error;
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index bf39d9c92201..0fc0b9135d46 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -228,6 +228,9 @@ struct nfs_server {
 	unsigned short		mountd_port;
 	unsigned short		mountd_protocol;
 	struct rpc_wait_queue	uoc_rpcwaitq;
+
+	/* XDR related information */
+	unsigned int		read_hdrsize;
 };
 
 /* Server capabilities */
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index bd1c889a9ed9..7f5535e5e852 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -608,6 +608,7 @@ struct nfs_pgio_args {
 	__u32			count;
 	unsigned int		pgbase;
 	struct page **		pages;
+	unsigned int		replen;		/* used by read */
 	const u32 *		bitmask;	/* used by write */
 	enum nfs3_stable_how	stable;		/* used by write */
 };
@@ -618,9 +619,9 @@ struct nfs_pgio_res {
 	__u32			count;
 	__u32			op_status;
 	int			eof;		/* used by read */
+	unsigned int		replen;		/* used by read */
 	struct nfs_writeverf *	verf;		/* used by write */
 	const struct nfs_server *server;	/* used by write */
-
 };
 
 /*
-- 
2.17.1

[PATCH 2/2] NFSv4: Save a few bytes in the nfs_pgio_args/res

[Trond Myklebust]

Save a few bytes by allowing the read/write specific fields of the
structures to share storage.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 include/linux/nfs_xdr.h | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 7f5535e5e852..7981498239f6 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -608,9 +608,13 @@ struct nfs_pgio_args {
 	__u32			count;
 	unsigned int		pgbase;
 	struct page **		pages;
-	unsigned int		replen;		/* used by read */
-	const u32 *		bitmask;	/* used by write */
-	enum nfs3_stable_how	stable;		/* used by write */
+	union {
+		unsigned int		replen;			/* used by read */
+		struct {
+			const u32 *		bitmask;	/* used by write */
+			enum nfs3_stable_how	stable;		/* used by write */
+		};
+	};
 };
 
 struct nfs_pgio_res {
@@ -618,10 +622,16 @@ struct nfs_pgio_res {
 	struct nfs_fattr *	fattr;
 	__u32			count;
 	__u32			op_status;
-	int			eof;		/* used by read */
-	unsigned int		replen;		/* used by read */
-	struct nfs_writeverf *	verf;		/* used by write */
-	const struct nfs_server *server;	/* used by write */
+	union {
+		struct {
+			int			eof;		/* used by read */
+			unsigned int		replen;		/* used by read */
+		};
+		struct {
+			struct nfs_writeverf *	verf;		/* used by write */
+			const struct nfs_server *server;	/* used by write */
+		};
+	};
 };
 
 /*
-- 
2.17.1

Re: [PATCH 1/2] NFSv3: Improve NFSv3 performance when server returns no post-op attributes

[kbuild test robot]

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Hi Trond,

I love your patch! Perhaps something to improve:

[auto build test WARNING on nfs/linux-next]
[also build test WARNING on v4.19-rc5 next-20180924]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Trond-Myklebust/NFSv3-Improve-NFSv3-performance-when-server-returns-no-post-op-attributes/20180925-122432
base:   git://git.linux-nfs.org/projects/trondmy/linux-nfs.git linux-next
config: i386-randconfig-x005-201838 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

   fs/nfs/nfs3xdr.c: In function 'nfs3_xdr_dec_read3res':
>> fs/nfs/nfs3xdr.c:1677:30: warning: initialization discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
     struct nfs_server *server = result->server;
                                 ^~~~~~
   fs/nfs/nfs3xdr.c:1678:15: warning: unused variable 'replen' [-Wunused-variable]
     unsigned int replen, pos;
                  ^~~~~~
   fs/nfs/nfs3xdr.c:1677:21: warning: unused variable 'server' [-Wunused-variable]
     struct nfs_server *server = result->server;
                        ^~~~~~

vim +/const +1677 fs/nfs/nfs3xdr.c

  1672	
  1673	static int nfs3_xdr_dec_read3res(struct rpc_rqst *req, struct xdr_stream *xdr,
  1674					 void *data)
  1675	{
  1676		struct nfs_pgio_res *result = data;
> 1677		struct nfs_server *server = result->server;
  1678		unsigned int replen, pos;
  1679		enum nfs_stat status;
  1680		int error;
  1681	
  1682		pos = xdr_stream_pos(xdr);
  1683		error = decode_nfsstat3(xdr, &status);
  1684		if (unlikely(error))
  1685			goto out;
  1686		error = decode_post_op_attr(xdr, result->fattr);
  1687		if (unlikely(error))
  1688			goto out;
  1689		result->op_status = status;
  1690		if (status != NFS3_OK)
  1691			goto out_status;
  1692		result->replen = 3 + ((xdr_stream_pos(xdr) - pos) >> 2);
  1693		error = decode_read3resok(xdr, result);
  1694	out:
  1695		return error;
  1696	out_status:
  1697		return nfs3_stat_to_errno(status);
  1698	}
  1699	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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