diff mbox series

NFS: Always provide aligned buffers to the RPC read layers

Message ID 20210827180056.610170-1-trondmy@kernel.org (mailing list archive)
State New, archived
Headers show
Series NFS: Always provide aligned buffers to the RPC read layers | expand

Commit Message

Trond Myklebust Aug. 27, 2021, 6 p.m. UTC 
From: Trond Myklebust <trond.myklebust@hammerspace.com>

Instead of messing around with XDR padding in the RDMA layer, we should
just give the RPC layer an aligned buffer. Try to avoid creating extra
RPC calls by aligning to the smaller value of ALIGN(len, rsize) and
PAGE_SIZE.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/read.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Dan Aloni Jan. 18, 2022, 7:26 p.m. UTC | #1 
On Fri, Aug 27, 2021 at 02:00:56PM -0400, trondmy@kernel.org wrote:
> From: Trond Myklebust <trond.myklebust@hammerspace.com>
> 
> Instead of messing around with XDR padding in the RDMA layer, we should
> just give the RPC layer an aligned buffer. Try to avoid creating extra
> RPC calls by aligning to the smaller value of ALIGN(len, rsize) and
> PAGE_SIZE.

I've bisected this change to be the cause of xfstests generic/525
getting stuck when tested against a standard Linux NFS server. It was
stuck in a repeated request loop in kernel mode, and killable.

I posted a patch with a full explanation in a reply.
diff mbox series

Patch

diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 9f39e0a1a38b..08d6cc57cbc3 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -293,15 +293,19 @@  static int
 readpage_async_filler(void *data, struct page *page)
 {
 	struct nfs_readdesc *desc = data;
+	struct inode *inode = page_file_mapping(page)->host;
+	unsigned int rsize = NFS_SERVER(inode)->rsize;
 	struct nfs_page *new;
-	unsigned int len;
+	unsigned int len, aligned_len;
 	int error;
 
 	len = nfs_page_length(page);
 	if (len == 0)
 		return nfs_return_empty_page(page);
 
-	new = nfs_create_request(desc->ctx, page, 0, len);
+	aligned_len = min_t(unsigned int, ALIGN(len, rsize), PAGE_SIZE);
+
+	new = nfs_create_request(desc->ctx, page, 0, aligned_len);
 	if (IS_ERR(new))
 		goto out_error;