From bfbfb6182ad1d7d184b16f25165faad879147f79 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 10 Sep 2022 22:14:02 +0100
Subject: [PATCH] nfsd_splice_actor(): handle compound pages
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>
---
fs/nfsd/vfs.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 9f486b788ed09..b16aed158ba63 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -846,10 +846,14 @@ 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;
+
+ page += offset / PAGE_SIZE;
+ for (int 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;
}
--
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