Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756816Ab3DOSRu (ORCPT ); Mon, 15 Apr 2013 14:17:50 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:58965 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756082Ab3DOSRt (ORCPT ); Mon, 15 Apr 2013 14:17:49 -0400 Date: Mon, 15 Apr 2013 19:17:40 +0100 From: Al Viro To: Miklos Szeredi Cc: Maxim Patlasov , dev@parallels.com, xemul@parallels.com, fuse-devel@lists.sourceforge.net, bfoster@redhat.com, linux-kernel@vger.kernel.org, devel@openvz.org, anand.avati@gmail.com Subject: Re: [PATCH 0/5] fuse: close file synchronously Message-ID: <20130415181739.GJ4068@ZenIV.linux.org.uk> References: <20121220122702.4101.80042.stgit@maximpc.sw.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1549 Lines: 30 On Mon, Apr 15, 2013 at 05:30:41PM +0200, Miklos Szeredi wrote: > On Mon, Apr 15, 2013 at 5:08 PM, Miklos Szeredi wrote: > > For example doing a readlink() on a magic symlink under /proc > > shouldn't result in a synchronous call to a fuse filesystem. Making > > fput() synchronous may actually end up doing that (even if it's not > > very likely). > > Thinking about this a bit more. As it is it sounds wrong to rely on a > synchronous release, when in fact release is just not synchronous, as > indicated by the above example. Maybe it's the proc code that's buggy > and shouldn't do get_file/fput because everyone is assuming release > being synchronous with close(). Don't know. What the hell? ->release() is not and has never been synchronous with close(). There is any number of places where the final fput() might be called and no, this readlink example is irrelevant - things like munmap()/dup2()/close of a socket discarding a datagram with the last reference to struct file in it, et sodding cetera. Hell, another thread might be in the middle of read(2) at the moment when you call close(). Result: the final fput() will be done when we are about to return from that read(2). People, ->release() is *NOT* guaranteed to be anywhere near close(2). Never had been. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/