From mboxrd@z Thu Jan 1 00:00:00 1970 References: <5D53D882.5090803@huawei.com> <20190819031537.GK52397@e18g06458.et15sqa> From: piaojun Message-ID: <5D5A1CD7.6070202@huawei.com> Date: Mon, 19 Aug 2019 11:51:51 +0800 MIME-Version: 1.0 In-Reply-To: <20190819031537.GK52397@e18g06458.et15sqa> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Subject: Re: [Virtio-fs] [PATCH][RFC] viriofsd: do not fall back to buffer io when cache=auto List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eryu Guan Cc: virtio-fs@redhat.com On 2019/8/19 11:15, Eryu Guan wrote: > On Wed, Aug 14, 2019 at 05:46:42PM +0800, piaojun wrote: >> Direct io flags will be tured off even if cache=auto, which seems a >> little bit strange. It's better to keep the open flags set by user. If >> I missed the discussion about this issue, please let me know, thanks. >> >> Signed-off-by: Jun Piao >> --- >> contrib/virtiofsd/passthrough_ll.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthrough_ll.c >> index 321bbb2..a080f0d 100644 >> --- a/contrib/virtiofsd/passthrough_ll.c >> +++ b/contrib/virtiofsd/passthrough_ll.c >> @@ -1687,6 +1687,8 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name, >> fi->direct_io = 1; >> else if (lo->cache == CACHE_ALWAYS) >> fi->keep_cache = 1; >> + else >> + fi->direct_io = !!(fi->flags & O_DIRECT); >> >> out: >> lo_inode_put(lo, &parent_inode); >> @@ -1899,6 +1901,8 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) >> fi->direct_io = 1; >> else if (lo->cache == CACHE_ALWAYS) >> fi->keep_cache = 1; >> + else >> + fi->direct_io = !!(fi->flags & O_DIRECT); >> fuse_reply_open(req, fi); > > IMHO, this is necessary, it seems that in the case cache=auto/always, > virtiofsd already follows what guest requests, i.e. virtiofsd only does > direct I/O when guest opens file with O_DIRECT. >>From my testing, virtiofsd won't do direct io even if guest opens file with O_DIRECT when cache=auto/alway. It's weird to convert direct io to buffer io at host side. > > If I understand the code correctly, fi->direct_io = 1 is used to force > guest to use direct I/O even if guest opens file without O_DIRECT. But in fact, direct I/O will be forced to buffer I/O even if with O_DIRECT. I will look into this problem by further testing, and very glad to share my test result. Jun