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From:   trondmy@kernel.org
To:     linux-nfs@vger.kernel.org
Subject: [PATCH 2/3] NFS: Avoid copy of xdr padding in readlink, layoutget and getxattr
Date:   Wed, 18 Nov 2020 17:19:38 -0500
Message-Id: <20201118221939.20715-2-trondmy@kernel.org>
In-Reply-To: <20201118221939.20715-1-trondmy@kernel.org>
References: <20201118221939.20715-1-trondmy@kernel.org>
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From: Trond Myklebust <trond.myklebust@hammerspace.com>

When doing a readlink, layoutget or getxattr call into an array of
pages, we don't care if the XDR padding ends up in the last page
when the data length is not 32-bit aligned.
Avoid an unnecessary copy by just leaving that padding in place.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/nfs2xdr.c  | 2 +-
 fs/nfs/nfs3xdr.c  | 2 +-
 fs/nfs/nfs42xdr.c | 2 +-
 fs/nfs/nfs4xdr.c  | 4 ++--
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index f6676af37d5d..db9c265ad9e1 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -437,7 +437,7 @@ static int decode_path(struct xdr_stream *xdr)
 	length = be32_to_cpup(p);
 	if (unlikely(length >= xdr->buf->page_len || length > NFS_MAXPATHLEN))
 		goto out_size;
-	recvd = xdr_read_pages(xdr, length);
+	recvd = xdr_read_pages(xdr, xdr_align_size(length));
 	if (unlikely(length > recvd))
 		goto out_cheating;
 	xdr_terminate_string(xdr->buf, length);
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index 69971f6c840d..d3e1726d538b 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -234,7 +234,7 @@ static int decode_nfspath3(struct xdr_stream *xdr)
 	count = be32_to_cpup(p);
 	if (unlikely(count >= xdr->buf->page_len || count > NFS3_MAXPATHLEN))
 		goto out_nametoolong;
-	recvd = xdr_read_pages(xdr, count);
+	recvd = xdr_read_pages(xdr, xdr_align_size(count));
 	if (unlikely(count > recvd))
 		goto out_cheating;
 	xdr_terminate_string(xdr->buf, count);
diff --git a/fs/nfs/nfs42xdr.c b/fs/nfs/nfs42xdr.c
index 6e060a88f98c..e58bfe208ae8 100644
--- a/fs/nfs/nfs42xdr.c
+++ b/fs/nfs/nfs42xdr.c
@@ -495,7 +495,7 @@ static int decode_getxattr(struct xdr_stream *xdr,
 	res->xattr_len = len;
 
 	if (len > 0) {
-		rdlen = xdr_read_pages(xdr, len);
+		rdlen = xdr_read_pages(xdr, xdr_align_size(len));
 		if (rdlen < len)
 			return -EIO;
 	}
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index c8714381d511..755b556e85c3 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -5250,7 +5250,7 @@ static int decode_readlink(struct xdr_stream *xdr, struct rpc_rqst *req)
 		dprintk("nfs: server returned giant symlink!\n");
 		return -ENAMETOOLONG;
 	}
-	recvd = xdr_read_pages(xdr, len);
+	recvd = xdr_read_pages(xdr, xdr_align_size(len));
 	if (recvd < len) {
 		dprintk("NFS: server cheating in readlink reply: "
 				"count %u > recvd %u\n", len, recvd);
@@ -5925,7 +5925,7 @@ static int decode_layoutget(struct xdr_stream *xdr, struct rpc_rqst *req,
 		res->type,
 		res->layoutp->len);
 
-	recvd = xdr_read_pages(xdr, res->layoutp->len);
+	recvd = xdr_read_pages(xdr, xdr_align_size(res->layoutp->len));
 	if (res->layoutp->len > recvd) {
 		dprintk("NFS: server cheating in layoutget reply: "
 				"layout len %u > recvd %u\n",
-- 
2.28.0