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Message-ID: <20130321164203.GC15740@arwen.pp.htv.fi>
Date: Thu, 21 Mar 2013 18:42:04 +0200
From: Felipe Balbi <balbi@...com>
To: Kent Overstreet <koverstreet@...gle.com>
CC: <linux-kernel@...r.kernel.org>, <linux-aio@...ck.org>,
<akpm@...ux-foundation.org>, Zach Brown <zab@...hat.com>,
Felipe Balbi <balbi@...com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Mark Fasheh <mfasheh@...e.com>,
Joel Becker <jlbec@...lplan.org>,
Rusty Russell <rusty@...tcorp.com.au>,
Jens Axboe <axboe@...nel.dk>,
Asai Thambi S P <asamymuthupa@...ron.com>,
Selvan Mani <smani@...ron.com>,
Sam Bradshaw <sbradshaw@...ron.com>,
Jeff Moyer <jmoyer@...hat.com>,
Al Viro <viro@...iv.linux.org.uk>,
Benjamin LaHaise <bcrl@...ck.org>,
"Theodore Ts'o" <tytso@....edu>,
Linux USB Mailing List <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 03/33] gadget: remove only user of aio retry
Hi,
On Thu, Mar 21, 2013 at 09:35:24AM -0700, Kent Overstreet wrote:
> From: Zach Brown <zab@...hat.com>
>
> This removes the only in-tree user of aio retry. This will let us remove
> the retry code from the aio core.
>
> Removing retry is relatively easy as the USB gadget wasn't using it to
> retry IOs at all. It always fully submitted the IO in the context of the
> initial io_submit() call. It only used the AIO retry facility to get the
> submitter's mm context for copying the result of a read back to user
> space. This is easy to implement with use_mm() and a work struct, much
> like kvm does with async_pf_execute() for get_user_pages().
>
> Signed-off-by: Zach Brown <zab@...hat.com>
> Signed-off-by: Kent Overstreet <koverstreet@...gle.com>
> Cc: Felipe Balbi <balbi@...com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Mark Fasheh <mfasheh@...e.com>
> Cc: Joel Becker <jlbec@...lplan.org>
> Cc: Rusty Russell <rusty@...tcorp.com.au>
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Asai Thambi S P <asamymuthupa@...ron.com>
> Cc: Selvan Mani <smani@...ron.com>
> Cc: Sam Bradshaw <sbradshaw@...ron.com>
> Cc: Jeff Moyer <jmoyer@...hat.com>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Benjamin LaHaise <bcrl@...ck.org>
> Cc: Theodore Ts'o <tytso@....edu>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
I don't have any objections with the approach. Let's see if anyone from
linux-usb has anything to say, though
> drivers/usb/gadget/inode.c | 38 +++++++++++++++++++++++++++++---------
> 1 file changed, 29 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
> index e2b2e9c..a1aad43 100644
> --- a/drivers/usb/gadget/inode.c
> +++ b/drivers/usb/gadget/inode.c
> @@ -24,6 +24,7 @@
> #include <linux/sched.h>
> #include <linux/slab.h>
> #include <linux/poll.h>
> +#include <linux/mmu_context.h>
>
> #include <linux/device.h>
> #include <linux/moduleparam.h>
> @@ -513,6 +514,9 @@ static long ep_ioctl(struct file *fd, unsigned code, unsigned long value)
> struct kiocb_priv {
> struct usb_request *req;
> struct ep_data *epdata;
> + struct kiocb *iocb;
> + struct mm_struct *mm;
> + struct work_struct work;
> void *buf;
> const struct iovec *iv;
> unsigned long nr_segs;
> @@ -540,15 +544,12 @@ static int ep_aio_cancel(struct kiocb *iocb, struct io_event *e)
> return value;
> }
>
> -static ssize_t ep_aio_read_retry(struct kiocb *iocb)
> +static ssize_t ep_copy_to_user(struct kiocb_priv *priv)
> {
> - struct kiocb_priv *priv = iocb->private;
> ssize_t len, total;
> void *to_copy;
> int i;
>
> - /* we "retry" to get the right mm context for this: */
> -
> /* copy stuff into user buffers */
> total = priv->actual;
> len = 0;
> @@ -568,9 +569,26 @@ static ssize_t ep_aio_read_retry(struct kiocb *iocb)
> if (total == 0)
> break;
> }
> +
> + return len;
> +}
> +
> +static void ep_user_copy_worker(struct work_struct *work)
> +{
> + struct kiocb_priv *priv = container_of(work, struct kiocb_priv, work);
> + struct mm_struct *mm = priv->mm;
> + struct kiocb *iocb = priv->iocb;
> + size_t ret;
> +
> + use_mm(mm);
> + ret = ep_copy_to_user(priv);
> + unuse_mm(mm);
> +
> + /* completing the iocb can drop the ctx and mm, don't touch mm after */
> + aio_complete(iocb, ret, ret);
> +
> kfree(priv->buf);
> kfree(priv);
> - return len;
> }
>
> static void ep_aio_complete(struct usb_ep *ep, struct usb_request *req)
> @@ -596,14 +614,14 @@ static void ep_aio_complete(struct usb_ep *ep, struct usb_request *req)
> aio_complete(iocb, req->actual ? req->actual : req->status,
> req->status);
> } else {
> - /* retry() won't report both; so we hide some faults */
> + /* ep_copy_to_user() won't report both; we hide some faults */
> if (unlikely(0 != req->status))
> DBG(epdata->dev, "%s fault %d len %d\n",
> ep->name, req->status, req->actual);
>
> priv->buf = req->buf;
> priv->actual = req->actual;
> - kick_iocb(iocb);
> + schedule_work(&priv->work);
> }
> spin_unlock(&epdata->dev->lock);
>
> @@ -633,8 +651,10 @@ fail:
> return value;
> }
> iocb->private = priv;
> + priv->iocb = iocb;
> priv->iv = iv;
> priv->nr_segs = nr_segs;
> + INIT_WORK(&priv->work, ep_user_copy_worker);
>
> value = get_ready_ep(iocb->ki_filp->f_flags, epdata);
> if (unlikely(value < 0)) {
> @@ -646,6 +666,7 @@ fail:
> get_ep(epdata);
> priv->epdata = epdata;
> priv->actual = 0;
> + priv->mm = current->mm; /* mm teardown waits for iocbs in exit_aio() */
>
> /* each kiocb is coupled to one usb_request, but we can't
> * allocate or submit those if the host disconnected.
> @@ -674,7 +695,7 @@ fail:
> kfree(priv);
> put_ep(epdata);
> } else
> - value = (iv ? -EIOCBRETRY : -EIOCBQUEUED);
> + value = -EIOCBQUEUED;
> return value;
> }
>
> @@ -692,7 +713,6 @@ ep_aio_read(struct kiocb *iocb, const struct iovec *iov,
> if (unlikely(!buf))
> return -ENOMEM;
>
> - iocb->ki_retry = ep_aio_read_retry;
> return ep_aio_rwtail(iocb, buf, iocb->ki_left, epdata, iov, nr_segs);
> }
>
> --
> 1.8.1.3
>
--
balbi
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