From mboxrd@z Thu Jan 1 00:00:00 1970 From: nick Subject: Re: [PATCH] f2fs crypto: add rwsem to avoid data races Date: Tue, 19 May 2015 10:35:30 -0400 Message-ID: <555B4A32.3000302@gmail.com> References: <1432013801-39069-1-git-send-email-jaegeuk@kernel.org> <20150519142943.GE20421@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Theodore Ts'o , Jaegeuk Kim , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Return-path: In-Reply-To: <20150519142943.GE20421@thunk.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net List-Id: linux-fsdevel.vger.kernel.org On 2015-05-19 10:29 AM, Theodore Ts'o wrote: > On Mon, May 18, 2015 at 10:36:41PM -0700, Jaegeuk Kim wrote: >> Previoulsy, fi->i_crypt_info was not covered by any lock, resulting in >> memory leak. >> >> This patch adds a rwsem to avoid leaking objects on i_crypt_info. >> >> Signed-off-by: Jaegeuk Kim > > I'm not sure we need an rwsem to fix this issue. In terms of > serializing the creation and deletion of the structure, it should be > possible to use an cmpxchg() on the pointer itself. (e.g., if we lose > the race on the creation side, we just release our structure and use > the one that the winner allocated). > > If we do end up needing to serialize access to the tfm in the > i_crypt_info object for datapath reads/writes, then we might need a > mutex, but I think that should be it, no? > > - Ted > > ------------------------------------------------------------------------------ > One dashboard for servers and applications across Physical-Virtual-Cloud > Widest out-of-the-box monitoring support with 50+ applications > Performance metrics, stats and reports that give you Actionable Insights > Deep dive visibility with transaction tracing using APM Insight. > http://ad.doubleclick.net/ddm/clk/290420510;117567292;y > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel > I have to agree with Ted here, as mutual exclusion locking is ideal for the scenario here of a reader vs writer exclusion. My only concern is that can there be many readers to one writer here as if so reader/writer spin locks may be better. Nick ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y