From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxim Patlasov Subject: Re: [PATCH 07/11] fuse: restructure fuse_readpage() Date: Mon, 20 Jan 2014 15:46:27 +0400 Message-ID: <52DD0C93.6010402@parallels.com> References: <20131010130718.10089.6736.stgit@dhcp-10-30-17-2.sw.ru> <20131010131113.10089.57270.stgit@dhcp-10-30-17-2.sw.ru> <20131112171707.GB10813@tucsk.piliscsaba.szeredi.hu> <52B45A30.10808@parallels.com> <20140106164319.GF16230@tucsk.piliscsaba.szeredi.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: , , , , , , , , , To: Miklos Szeredi Return-path: Received: from relay.parallels.com ([195.214.232.42]:43715 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750738AbaATLqa (ORCPT ); Mon, 20 Jan 2014 06:46:30 -0500 In-Reply-To: <20140106164319.GF16230@tucsk.piliscsaba.szeredi.hu> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 01/06/2014 08:43 PM, Miklos Szeredi wrote: > On Fri, Dec 20, 2013 at 06:54:40PM +0400, Maxim Patlasov wrote: >> Hi Miklos, >> >> Sorry for delay, see please inline comments below. >> >> On 11/12/2013 09:17 PM, Miklos Szeredi wrote: >>> On Thu, Oct 10, 2013 at 05:11:25PM +0400, Maxim Patlasov wrote: >>>> Move the code filling and sending read request to a separate function. Future >>>> patches will use it for .write_begin -- partial modification of a page >>>> requires reading the page from the storage very similarly to what fuse_readpage >>>> does. >>>> >>>> Signed-off-by: Maxim Patlasov >>>> --- >>>> fs/fuse/file.c | 55 +++++++++++++++++++++++++++++++++++++------------------ >>>> 1 file changed, 37 insertions(+), 18 deletions(-) >>>> >>>> diff --git a/fs/fuse/file.c b/fs/fuse/file.c >>>> index b4d4189..77eb849 100644 >>>> --- a/fs/fuse/file.c >>>> +++ b/fs/fuse/file.c >>>> @@ -700,21 +700,14 @@ static void fuse_short_read(struct fuse_req *req, struct inode *inode, >>>> } >>>> } >>>> -static int fuse_readpage(struct file *file, struct page *page) >>>> +static int __fuse_readpage(struct file *file, struct page *page, size_t count, >>>> + int *err, struct fuse_req **req_pp, u64 *attr_ver_p) >>> Signature of this helper looks really ugly. A quick look tells me that neither >>> caller actually needs 'req'. >> fuse_readpage() passes 'req' to fuse_short_read(). And the latter >> uses req->pages[] to nullify a part of request. > I don't get it. __fuse_readpage() itself call's fuse_short_read(), not callers > of __fuse_readpage(). Or do they? fuse_readpage() is a caller of __fuse_readpage() and it looks (after applying the patch) like this: > static int fuse_readpage(struct file *file, struct page *page) > { > ... > num_read = __fuse_readpage(file, page, count, &err, &req, &attr_ver); > if (!err) { > /* > * Short read means EOF. If file size is larger, truncate it > */ > if (num_read < count) > fuse_short_read(req, inode, attr_ver); > > SetPageUptodate(page); > } Thanks, Maxim > >>> And fuse_get_attr_version() can be moved to the >>> one caller that needs it. >> Yes, it's doable. But this would make attr_version mechanism less >> efficient (under some loads): suppose the file on server was >> truncated externally, then fuse_readpage() acquires >> fc->attr_version, then some innocent write bumps fc->attr_version >> while we're waiting for fuse writeback, then fuse_read_update_size() >> would noop. In the other words, it's beneficial to keep the time >> interval between acquiring fc->attr_version and subsequent >> comparison as short as possible. > Okay, lets try to keep this the way it is. I don't like it very much, but I > fear changing user visible behavior. > > Thanks, > Miklos >