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From:   Olga Kornievskaia <olga.kornievskaia@gmail.com>
To:     trond.myklebust@hammerspace.com, anna.schumaker@netapp.com
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH 1/1] pNFS/filelayout: Fix coalescing test for single DS
Date:   Tue, 20 Dec 2022 11:29:12 -0500
Message-Id: <20221220162912.95886-1-olga.kornievskaia@gmail.com>
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When there is a single DS no striping constraints need to be placed on
the IO. When such constraint is applied then buffered reads don't
coalesce to the DS's rsize.

Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
---
 fs/nfs/filelayout/filelayout.c    | 2 ++
 fs/nfs/filelayout/filelayout.h    | 1 +
 fs/nfs/filelayout/filelayoutdev.c | 4 +++-
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/filelayout/filelayout.c b/fs/nfs/filelayout/filelayout.c
index ad34a33b0737..cd819b795935 100644
--- a/fs/nfs/filelayout/filelayout.c
+++ b/fs/nfs/filelayout/filelayout.c
@@ -803,6 +803,8 @@ filelayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
 	size = pnfs_generic_pg_test(pgio, prev, req);
 	if (!size)
 		return 0;
+	else if (FILELAYOUT_LSEG(pgio->pg_lseg)->single_ds)
+		return size;
 
 	/* see if req and prev are in the same stripe */
 	if (prev) {
diff --git a/fs/nfs/filelayout/filelayout.h b/fs/nfs/filelayout/filelayout.h
index aed0748fd6ec..524920c2cbf8 100644
--- a/fs/nfs/filelayout/filelayout.h
+++ b/fs/nfs/filelayout/filelayout.h
@@ -65,6 +65,7 @@ struct nfs4_filelayout_segment {
 	struct nfs4_file_layout_dsaddr	*dsaddr; /* Point to GETDEVINFO data */
 	unsigned int			num_fh;
 	struct nfs_fh			**fh_array;
+	bool				single_ds;
 };
 
 struct nfs4_filelayout {
diff --git a/fs/nfs/filelayout/filelayoutdev.c b/fs/nfs/filelayout/filelayoutdev.c
index acf4b88889dc..95ebbe9e7ed4 100644
--- a/fs/nfs/filelayout/filelayoutdev.c
+++ b/fs/nfs/filelayout/filelayoutdev.c
@@ -243,8 +243,10 @@ nfs4_fl_select_ds_fh(struct pnfs_layout_segment *lseg, u32 j)
 	u32 i;
 
 	if (flseg->stripe_type == STRIPE_SPARSE) {
-		if (flseg->num_fh == 1)
+		if (flseg->num_fh == 1) {
+			flseg->single_ds = true;
 			i = 0;
+		}
 		else if (flseg->num_fh == 0)
 			/* Use the MDS OPEN fh set in nfs_read_rpcsetup */
 			return NULL;
-- 
2.31.1