Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934272Ab3E1V0b (ORCPT ); Tue, 28 May 2013 17:26:31 -0400 Received: from mail-pa0-f50.google.com ([209.85.220.50]:63726 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933709Ab3E1V0Z (ORCPT ); Tue, 28 May 2013 17:26:25 -0400 From: Kent Overstreet To: torvalds@linux-foundation.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-aio@kvack.org Cc: Kent Overstreet , 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 , Benjamin LaHaise Subject: [PATCH] aio: Use call_rcu() instead of synchronize_rcu() in kill_ioctx() Date: Tue, 28 May 2013 14:26:18 -0700 Message-Id: <1369776378-27921-1-git-send-email-koverstreet@google.com> X-Mailer: git-send-email 1.8.2.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3132 Lines: 101 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 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 -- 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/