On Dec 20, 2022, at 12:31, Olga Kornievskaia [off-list ref] wrote:

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 <redacted>
---
fs/nfs/filelayout/filelayout.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/fs/nfs/filelayout/filelayout.c b/fs/nfs/filelayout/filelayout.c
index ad34a33b0737..4974cd18ca46 100644
--- a/fs/nfs/filelayout/filelayout.c
+++ b/fs/nfs/filelayout/filelayout.c

@@ -783,6 +783,12 @@ filelayout_alloc_lseg(struct pnfs_layout_hdr *layoutid,

return &fl->generic_hdr;
}

+static bool
+filelayout_lseg_is_striped(const struct nfs4_filelayout_segment *flseg)
+{
+ return flseg->num_fh > 1;
+}
+
/*
 * filelayout_pg_test(). Called by nfs_can_coalesce_requests()
 *

@@ -803,6 +809,8 @@ 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_is_striped(FILELAYOUT_LSEG(pgio->pg_lseg)))
+ return size;

/* see if req and prev are in the same stripe */
if (prev) {
-- 
2.31.1