Linux 5.15.154

[thirdparty/kernel/stable-queue.git] / releases / 5.15.154 / nfsd_splice_actor-handle-compound-pages.patch

From 39db3090791509dadb896ad8a1d1cebefed7c733 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Sat, 10 Sep 2022 22:14:02 +0100
Subject: nfsd_splice_actor(): handle compound pages

From: Al Viro <viro@zeniv.linux.org.uk>

[ Upstream commit bfbfb6182ad1d7d184b16f25165faad879147f79 ]

pipe_buffer might refer to a compound page (and contain more than a PAGE_SIZE
worth of data).  Theoretically it had been possible since way back, but
nfsd_splice_actor() hadn't run into that until copy_page_to_iter() change.
Fortunately, the only thing that changes for compound pages is that we
need to stuff each relevant subpage in and convert the offset into offset
in the first subpage.

Acked-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Benjamin Coddington <bcodding@redhat.com>
Fixes: f0f6b614f83d "copy_page_to_iter(): don't split high-order page in case of ITER_PIPE"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/vfs.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index ad689215b1f37..343af6341e5e1 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -846,10 +846,15 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 		  struct splice_desc *sd)
 {
 	struct svc_rqst *rqstp = sd->u.data;
-
-	svc_rqst_replace_page(rqstp, buf->page);
-	if (rqstp->rq_res.page_len == 0)
-		rqstp->rq_res.page_base = buf->offset;
+	struct page *page = buf->page;	// may be a compound one
+	unsigned offset = buf->offset;
+	int i;
+
+	page += offset / PAGE_SIZE;
+	for (i = sd->len; i > 0; i -= PAGE_SIZE)
+		svc_rqst_replace_page(rqstp, page++);
+	if (rqstp->rq_res.page_len == 0)	// first call
+		rqstp->rq_res.page_base = offset % PAGE_SIZE;
 	rqstp->rq_res.page_len += sd->len;
 	return sd->len;
 }
-- 
2.43.0