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 572FCC7EE45 for ; Thu, 8 Jun 2023 07:17:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234276AbjFHHRd (ORCPT ); Thu, 8 Jun 2023 03:17:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233688AbjFHHRS (ORCPT ); Thu, 8 Jun 2023 03:17:18 -0400 Received: from out-44.mta0.migadu.com (out-44.mta0.migadu.com [91.218.175.44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BD5B211F for ; Thu, 8 Jun 2023 00:17:16 -0700 (PDT) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1686208635; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PYaxIE7drJ+/TJJv2q7eZno6OBcQyD/ucHHPYyFGpK4=; b=wkJNRJHLbh9aQ4unHXMUUmMjaeBcXs/qFR3Rs4KyovmLF+kdicnLN+R7RHFxZR8gPOeUp9 NX2P+REnUEJ34GOGBJdqlnL4r3MWIn5sufjigvIydnRKgqwEVvKiVeSEw5Vpc0fYi1EekM GtzdXjz0W+Gt6CipwVe6wb8Pthy8PJw= Date: Thu, 8 Jun 2023 15:17:03 +0800 MIME-Version: 1.0 Subject: Re: [PATCH] fuse: add a new flag to allow shared mmap in FOPEN_DIRECT_IO mode X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Hao Xu To: fuse-devel@lists.sourceforge.net Cc: miklos@szeredi.hu, bernd.schubert@fastmail.fm, linux-fsdevel@vger.kernel.org References: <20230505081652.43008-1-hao.xu@linux.dev> Content-Language: en-US In-Reply-To: <20230505081652.43008-1-hao.xu@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org ping... On 5/5/23 16:16, Hao Xu wrote: > 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