[PATCH 1/2] shmem: Fix splice of a missing page

[David Howells <dhowells@redhat.com>]

Fix shmem_splice_read() to splice only part of the partial page at the end
of a splice and not all of it.

This can be seen by splicing from a tmpfs file that's not a multiple of
PAGE_SIZE in size.  Without this fix, it splices extra data to round up to
PAGE_SIZE.

Fixes: bd194b187115 ("shmem: Implement splice-read")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Hugh Dickins <hughd@google.com>
cc: Christoph Hellwig <hch@lst.de>
cc: Jens Axboe <axboe@kernel.dk>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: John Hubbard <jhubbard@nvidia.com>
cc: David Hildenbrand <david@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: Chuck Lever <chuck.lever@oracle.com>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---
 mm/shmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 2f2e0e618072..0164cccdcd71 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2841,7 +2841,7 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
 			folio_put(folio);
 			folio = NULL;
 		} else {
-			n = splice_zeropage_into_pipe(pipe, *ppos, len);
+			n = splice_zeropage_into_pipe(pipe, *ppos, part);
 		}
 
 		if (!n)