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 <koverstr...@google.com>
Signed-off-by: Benjamin LaHaise <b...@kvack.org>
Tested-by: Benjamin LaHaise <b...@kvack.org>
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 <z...@redhat.com>
> Cc: Felipe Balbi <ba...@ti.com>
> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
> Cc: Mark Fasheh <mfas...@suse.com>
> Cc: Joel Becker <jl...@evilplan.org>
> Cc: Rusty Russell <ru...@rustcorp.com.au>
> Cc: Jens Axboe <ax...@kernel.dk>
> Cc: Asai Thambi S P <asamymuth...@micron.com>
> Cc: Selvan Mani <sm...@micron.com>
> Cc: Sam Bradshaw <sbrads...@micron.com>
> Cc: Jeff Moyer <jmo...@redhat.com>
> Cc: Al Viro <v...@zeniv.linux.org.uk>
> Cc: Benjamin LaHaise <b...@kvack.org>
> ---
> 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."
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