Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754151AbaF0U5M (ORCPT ); Fri, 27 Jun 2014 16:57:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35343 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752936AbaF0U5K (ORCPT ); Fri, 27 Jun 2014 16:57:10 -0400 Date: Fri, 27 Jun 2014 16:56:54 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Mike Snitzer 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 In-Reply-To: <20140627192904.GA21254@redhat.com> Message-ID: References: <1403841690-4401-1-git-send-email-huangminfei@ucloud.cn> <20140627151105.GA30592@debian> <20140627192904.GA21254@redhat.com> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 Jun 2014, Mike Snitzer wrote: > 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): Acked-by: Mikulas Patocka > 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/