Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752280AbaF0T3Q (ORCPT ); Fri, 27 Jun 2014 15:29:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55971 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750714AbaF0T3P (ORCPT ); Fri, 27 Jun 2014 15:29:15 -0400 Date: Fri, 27 Jun 2014 15:29:04 -0400 From: Mike Snitzer To: Mikulas Patocka Cc: Joe Thornber , device-mapper development , linux-kernel@vger.kernel.org, Minfei Huang , linux-raid@vger.kernel.org, agk@redhat.com Subject: Re: dm-io: Prevent the danging point of the sync io callback function Message-ID: <20140627192904.GA21254@redhat.com> References: <1403841690-4401-1-git-send-email-huangminfei@ucloud.cn> <20140627151105.GA30592@debian> 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 On Fri, Jun 27 2014 at 2:44pm -0400, Mikulas Patocka wrote: > > > On Fri, 27 Jun 2014, Joe Thornber wrote: > > > On Fri, Jun 27, 2014 at 12:01:30PM +0800, Minfei Huang wrote: > > > The io address in callback function will become the danging point, > > > cause by the thread of sync io wakes up by other threads > > > and return to relieve the io address, > > > > Yes, well found. I prefer the following fix however. > > > > - Joe > > It seems ok. > > The patch is too big, I think the only change that needs to be done to fix > the bug is to replace "struct task_struct *sleeper;" with "struct > completion *completion;", replace "if (io->sleeper) > wake_up_process(io->sleeper);" with "if (io->completion) > complete(io->completion);" and declare the completion in sync_io() and > wait on it instead of "while (1)" loop there. Here is the minimalist fix you suggested (I agree that splitting out a minimalist fix is useful): drivers/md/dm-io.c | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-) diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c index 2a20986..e60c2ea 100644 --- a/drivers/md/dm-io.c +++ b/drivers/md/dm-io.c @@ -10,6 +10,7 @@ #include #include +#include #include #include #include @@ -32,7 +33,7 @@ struct dm_io_client { struct io { unsigned long error_bits; atomic_t count; - struct task_struct *sleeper; + struct completion *wait; struct dm_io_client *client; io_notify_fn callback; void *context; @@ -121,8 +122,8 @@ static void dec_count(struct io *io, unsigned int region, int error) invalidate_kernel_vmap_range(io->vma_invalidate_address, io->vma_invalidate_size); - if (io->sleeper) - wake_up_process(io->sleeper); + if (io->wait) + complete(io->wait); else { unsigned long r = io->error_bits; @@ -385,6 +386,7 @@ static int sync_io(struct dm_io_client *client, unsigned int num_regions, */ volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1]; struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io)); + DECLARE_COMPLETION_ONSTACK(wait); if (num_regions > 1 && (rw & RW_MASK) != WRITE) { WARN_ON(1); @@ -393,7 +395,7 @@ static int sync_io(struct dm_io_client *client, unsigned int num_regions, io->error_bits = 0; atomic_set(&io->count, 1); /* see dispatch_io() */ - io->sleeper = current; + io->wait = &wait; io->client = client; io->vma_invalidate_address = dp->vma_invalidate_address; @@ -401,15 +403,7 @@ static int sync_io(struct dm_io_client *client, unsigned int num_regions, dispatch_io(rw, num_regions, where, dp, io, 1); - while (1) { - set_current_state(TASK_UNINTERRUPTIBLE); - - if (!atomic_read(&io->count)) - break; - - io_schedule(); - } - set_current_state(TASK_RUNNING); + wait_for_completion_io(&wait); if (error_bits) *error_bits = io->error_bits; @@ -432,7 +426,7 @@ static int async_io(struct dm_io_client *client, unsigned int num_regions, io = mempool_alloc(client->pool, GFP_NOIO); io->error_bits = 0; atomic_set(&io->count, 1); /* see dispatch_io() */ - io->sleeper = NULL; + io->wait = NULL; io->client = client; io->callback = fn; io->context = context; -- 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/