[RFC PATCH 2/6] nfsd: Coalesce contiguous pages for direct reads

[J Louis Kaplan <Louis.Kaplan@arm.com>]

Use the previously added helper functions for nfsd direct read buffers.

Before this change, the direct-read path builds one bvec per base page,
even when the destination pages are physically contiguous.

Coalesce these pages into multipage bvecs to reduce the number of
entries traversed when advancing the filesystem's read iterator.

Signed-off-by: J Louis Kaplan <Louis.Kaplan@arm.com>
Assisted-by: LLM
---
 fs/nfsd/vfs.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index c7dd94697f2ff..329bb7d410765 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1124,11 +1124,16 @@ nfsd_direct_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	v = 0;
 	total = dio_end - dio_start;
 	while (total && v < rqstp->rq_maxpages && page < rqstp->rq_page_end) {
-		len = min_t(size_t, total, PAGE_SIZE);
-		bvec_set_page(&rqstp->rq_bvec[v], *page, len, 0);
+		len = svc_pages_to_bvec(&rqstp->rq_bvec[v],
+					page,
+					rqstp->rq_page_end - page,
+					0, min_t(size_t, total, UINT_MAX),
+					UINT_MAX);
+		if (!len)
+			break;
 
 		total -= len;
-		++page;
+		page += DIV_ROUND_UP(len, PAGE_SIZE);
 		++v;
 	}
 	rqstp->rq_next_page = page;
-- 
2.43.0