From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F433C77B7C for ; Fri, 5 May 2023 08:17:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229789AbjEEIRI (ORCPT ); Fri, 5 May 2023 04:17:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49650 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229810AbjEEIRG (ORCPT ); Fri, 5 May 2023 04:17:06 -0400 Received: from out-46.mta0.migadu.com (out-46.mta0.migadu.com [IPv6:2001:41d0:1004:224b::2e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5A8DD160B0 for ; Fri, 5 May 2023 01:17:04 -0700 (PDT) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1683274619; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=nT7kQry8oHMnNXnvgQgPuRtK/YcDHASPdexri6qXCeY=; b=w2DKtyJ4l0xDE+JVYJERr5hrlLjBAIMm7wsx66xpPqPLUtrofhZP8vbHIaKi9F1SGUX3GM ED0i9fSk0niKM44H+jYBhyztb8j1luL1Hwz0FN7W3bbsmFJ4dAC17/nc7Q6gUUj91ebTQv sv9b5G+AERswfpCa+holwoeiS5nEbTU= From: Hao Xu To: fuse-devel@lists.sourceforge.net Cc: miklos@szeredi.hu, bernd.schubert@fastmail.fm, linux-fsdevel@vger.kernel.org Subject: [PATCH] fuse: add a new flag to allow shared mmap in FOPEN_DIRECT_IO mode Date: Fri, 5 May 2023 16:16:52 +0800 Message-Id: <20230505081652.43008-1-hao.xu@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Hao Xu FOPEN_DIRECT_IO is usually set by fuse daemon to indicate need of strong coherency, e.g. network filesystems. Thus shared mmap is disabled since it leverages page cache and may write to it, which may cause inconsistence. But FOPEN_DIRECT_IO can be used not for coherency but to reduce memory footprint as well, e.g. reduce guest memory usage with virtiofs. Therefore, add a new flag FOPEN_DIRECT_IO_SHARED_MMAP to allow shared mmap for these cases. Signed-off-by: Hao Xu --- fs/fuse/file.c | 11 ++++++++--- include/uapi/linux/fuse.h | 2 ++ 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 89d97f6188e0..655896bdb0d5 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -161,7 +161,8 @@ struct fuse_file *fuse_file_open(struct fuse_mount *fm, u64 nodeid, } if (isdir) - ff->open_flags &= ~FOPEN_DIRECT_IO; + ff->open_flags &= + ~(FOPEN_DIRECT_IO | FOPEN_DIRECT_IO_SHARED_MMAP); ff->nodeid = nodeid; @@ -2509,8 +2510,12 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma) return fuse_dax_mmap(file, vma); if (ff->open_flags & FOPEN_DIRECT_IO) { - /* Can't provide the coherency needed for MAP_SHARED */ - if (vma->vm_flags & VM_MAYSHARE) + /* Can't provide the coherency needed for MAP_SHARED. + * So disable it if FOPEN_DIRECT_IO_SHARED_MMAP is not + * set, which means we do need strong coherency. + */ + if (!(ff->open_flags & FOPEN_DIRECT_IO_SHARED_MMAP) && + vma->vm_flags & VM_MAYSHARE) return -ENODEV; invalidate_inode_pages2(file->f_mapping); diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index 1b9d0dfae72d..003dcf42e8c2 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -314,6 +314,7 @@ struct fuse_file_lock { * FOPEN_STREAM: the file is stream-like (no file position at all) * FOPEN_NOFLUSH: don't flush data cache on close (unless FUSE_WRITEBACK_CACHE) * FOPEN_PARALLEL_DIRECT_WRITES: Allow concurrent direct writes on the same inode + * FOPEN_DIRECT_IO_SHARED_MMAP: allow shared mmap when FOPEN_DIRECT_IO is set */ #define FOPEN_DIRECT_IO (1 << 0) #define FOPEN_KEEP_CACHE (1 << 1) @@ -322,6 +323,7 @@ struct fuse_file_lock { #define FOPEN_STREAM (1 << 4) #define FOPEN_NOFLUSH (1 << 5) #define FOPEN_PARALLEL_DIRECT_WRITES (1 << 6) +#define FOPEN_DIRECT_IO_SHARED_MMAP (1 << 7) /** * INIT request/reply flags -- 2.25.1