Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759187Ab3E1XK0 (ORCPT ); Tue, 28 May 2013 19:10:26 -0400 Received: from kanga.kvack.org ([205.233.56.17]:55900 "EHLO kanga.kvack.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758201Ab3E1XKZ (ORCPT ); Tue, 28 May 2013 19:10:25 -0400 Date: Tue, 28 May 2013 19:10:24 -0400 From: Benjamin LaHaise To: Kent Overstreet Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-aio@kvack.org, Zach Brown , Felipe Balbi , Greg Kroah-Hartman , Mark Fasheh , Joel Becker , Rusty Russell , Jens Axboe , Asai Thambi S P , Selvan Mani , Sam Bradshaw , Jeff Moyer , Al Viro Subject: Re: [PATCH] aio: Use call_rcu() instead of synchronize_rcu() in kill_ioctx() Message-ID: <20130528231024.GA24189@kvack.org> References: <1369776378-27921-1-git-send-email-koverstreet@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1369776378-27921-1-git-send-email-koverstreet@google.com> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3680 Lines: 113 On Tue, May 28, 2013 at 02:26:18PM -0700, Kent Overstreet wrote: > Just making ioctx shutdown asynchronous so as not to block io_destroy() > - and percpu refcounts for the ioctx are going to need a RCU barrier in > the same place anyways. > > Signed-off-by: Kent Overstreet Signed-off-by: Benjamin LaHaise Tested-by: Benjamin LaHaise I have reviewed and tested this, and it fixes the io_setup() returning EAGAIN error from the first version of this patch. Thanks Kent! -ben > Cc: Zach Brown > Cc: Felipe Balbi > Cc: Greg Kroah-Hartman > Cc: Mark Fasheh > Cc: Joel Becker > Cc: Rusty Russell > Cc: Jens Axboe > Cc: Asai Thambi S P > Cc: Selvan Mani > Cc: Sam Bradshaw > Cc: Jeff Moyer > Cc: Al Viro > Cc: Benjamin LaHaise > --- > fs/aio.c | 36 ++++++++++++++++-------------------- > 1 file changed, 16 insertions(+), 20 deletions(-) > > diff --git a/fs/aio.c b/fs/aio.c > index 7fe5bde..2bbcacf 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -141,9 +141,6 @@ static void aio_free_ring(struct kioctx *ctx) > for (i = 0; i < ctx->nr_pages; i++) > put_page(ctx->ring_pages[i]); > > - if (ctx->mmap_size) > - vm_munmap(ctx->mmap_base, ctx->mmap_size); > - > if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages) > kfree(ctx->ring_pages); > } > @@ -322,11 +319,6 @@ static void free_ioctx(struct kioctx *ctx) > > aio_free_ring(ctx); > > - spin_lock(&aio_nr_lock); > - BUG_ON(aio_nr - ctx->max_reqs > aio_nr); > - aio_nr -= ctx->max_reqs; > - spin_unlock(&aio_nr_lock); > - > pr_debug("freeing %p\n", ctx); > > /* > @@ -435,17 +427,24 @@ static void kill_ioctx(struct kioctx *ctx) > { > if (!atomic_xchg(&ctx->dead, 1)) { > hlist_del_rcu(&ctx->list); > - /* Between hlist_del_rcu() and dropping the initial ref */ > - synchronize_rcu(); > > /* > - * We can't punt to workqueue here because put_ioctx() -> > - * free_ioctx() will unmap the ringbuffer, and that has to be > - * done in the original process's context. kill_ioctx_rcu/work() > - * exist for exit_aio(), as in that path free_ioctx() won't do > - * the unmap. > + * It'd be more correct to do this in free_ioctx(), after all > + * the outstanding kiocbs have finished - but by then io_destroy > + * has already returned, so io_setup() could potentially return > + * -EAGAIN with no ioctxs actually in use (as far as userspace > + * could tell). > */ > - kill_ioctx_work(&ctx->rcu_work); > + spin_lock(&aio_nr_lock); > + BUG_ON(aio_nr - ctx->max_reqs > aio_nr); > + aio_nr -= ctx->max_reqs; > + spin_unlock(&aio_nr_lock); > + > + if (ctx->mmap_size) > + vm_munmap(ctx->mmap_base, ctx->mmap_size); > + > + /* Between hlist_del_rcu() and dropping the initial ref */ > + call_rcu(&ctx->rcu_head, kill_ioctx_rcu); > } > } > > @@ -495,10 +494,7 @@ void exit_aio(struct mm_struct *mm) > */ > ctx->mmap_size = 0; > > - if (!atomic_xchg(&ctx->dead, 1)) { > - hlist_del_rcu(&ctx->list); > - call_rcu(&ctx->rcu_head, kill_ioctx_rcu); > - } > + kill_ioctx(ctx); > } > } > > -- > 1.8.2.1 -- "Thought is the essence of where you are now." -- 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/