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Registered in England and Wales under Company Registration No. 3798903 From: David Howells To: Jens Axboe , Matthew Wilcox , Miklos Szeredi , Amit Shah cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [RFC][PATCH v2] splice: Prevent gifting of multipage folios MIME-Version: 1.0 Content-ID: <2740800.1677513063.1@warthog.procyon.org.uk> Date: Mon, 27 Feb 2023 15:51:03 +0000 Message-ID: <2740801.1677513063@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1759001261063139893?= X-GMAIL-MSGID: =?utf-8?q?1759001474225023802?= Don't let parts of compound pages/multipage folios be gifted by (vm)splice into a pipe as the other end may only be expecting single-page gifts (fuse and virtio console for example). replace_page_cache_folio(), for example, will do the wrong thing if it tries to replace a single paged folio with a multipage folio. Try to avoid this by making add_to_pipe() remove the gift flag on multipage folios. Fixes: 7afa6fd037e5 ("[PATCH] vmsplice: allow user to pass in gift pages") Signed-off-by: David Howells cc: Matthew Wilcox cc: Jens Axboe cc: Miklos Szeredi cc: Amit Shah cc: linux-fsdevel@vger.kernel.org cc: virtualization@lists.linux-foundation.org cc: linux-mm@kvack.org --- fs/splice.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/splice.c b/fs/splice.c index 2e76dbb81a8f..8bbd7794d9f0 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -240,6 +240,8 @@ ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf) } else if (pipe_full(head, tail, pipe->max_usage)) { ret = -EAGAIN; } else { + if (PageCompound(buf->page)) + buf->flags &= ~PIPE_BUF_FLAG_GIFT; pipe->bufs[head & mask] = *buf; pipe->head = head + 1; return buf->len;