Re: [PATCH v2 1/5] nbd: fix might_sleep warning on socket shutdown.

[Pranay Srivastava <pranjas@gmail.com>]

Hello,

On Thu, Jun 9, 2016 at 3:33 PM, Pranay Srivastava <pranjas@gmail.com> wrote:
>
> Hello
>
>
> On Thu, Jun 2, 2016 at 3:54 PM, Pranay Kr. Srivastava <pranjas@gmail.com> wrote:
> > spinlocked ranges should be small and not contain calls into huge
> > subfunctions. Fix my mistake and just get the pointer to the socket
> > instead of doing everything with spinlock held.
> >
> > Reported-by: Mikulas Patocka <mikulas@twibright.com>
> > Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
> >
> > Changelog:
> > Pranay Kr. Srivastava<pranjas@gmail.com>:
> >
> > 1) Use spin_lock instead of irq version for sock_shutdown.
> >
> > 2) Use system work queue to actually trigger the shutdown of
> >    socket. This solves the issue when kernel_sendmsg is currently
> >    blocked while a timeout occurs.
> >
> > Signed-off-by: Pranay Kr. Srivastava <pranjas@gmail.com>
> > ---
> >  drivers/block/nbd.c | 65 ++++++++++++++++++++++++++++++++++-------------------
> >  1 file changed, 42 insertions(+), 23 deletions(-)
> >
> > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> > index 31e73a7..0339d40 100644
> > --- a/drivers/block/nbd.c
> > +++ b/drivers/block/nbd.c
> > @@ -39,6 +39,7 @@
> >  #include <asm/types.h>
> >
> >  #include <linux/nbd.h>
> > +#include <linux/workqueue.h>
> >
> >  struct nbd_device {
> >         u32 flags;
> > @@ -69,6 +70,10 @@ struct nbd_device {
> >  #if IS_ENABLED(CONFIG_DEBUG_FS)
> >         struct dentry *dbg_dir;
> >  #endif
> > +       /*
> > +        *This is specifically for calling sock_shutdown, for now.
> > +        */
> > +       struct work_struct ws_shutdown;
> >  };
> >
> >  #if IS_ENABLED(CONFIG_DEBUG_FS)
> > @@ -95,6 +100,11 @@ static int max_part;
> >   */
> >  static DEFINE_SPINLOCK(nbd_lock);
> >
> > +/*
> > + * Shutdown function for nbd_dev work struct.
> > + */
> > +static void nbd_ws_func_shutdown(struct work_struct *);
> > +
> >  static inline struct device *nbd_to_dev(struct nbd_device *nbd)
> >  {
> >         return disk_to_dev(nbd->disk);
> > @@ -172,39 +182,35 @@ static void nbd_end_request(struct nbd_device *nbd, struct request *req)
> >   */
> >  static void sock_shutdown(struct nbd_device *nbd)
> >  {
> > -       spin_lock_irq(&nbd->sock_lock);
> > -
> > -       if (!nbd->sock) {
> > -               spin_unlock_irq(&nbd->sock_lock);
> > -               return;
> > -       }
> > +       struct socket *sock;
> >
> > -       dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n");
> > -       kernel_sock_shutdown(nbd->sock, SHUT_RDWR);
> > -       sockfd_put(nbd->sock);
> > +       spin_lock(&nbd->sock_lock);
> > +       sock = nbd->sock;
> >         nbd->sock = NULL;
> > -       spin_unlock_irq(&nbd->sock_lock);
> > +       spin_unlock(&nbd->sock_lock);
> > +
> > +       if (!sock)
> > +               return;
> >
> >         del_timer(&nbd->timeout_timer);
> > +       dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n");
> > +       kernel_sock_shutdown(sock, SHUT_RDWR);
> > +       sockfd_put(sock);
> >  }
> >
> >  static void nbd_xmit_timeout(unsigned long arg)
> >  {
> >         struct nbd_device *nbd = (struct nbd_device *)arg;
> > -       unsigned long flags;
> >
> >         if (list_empty(&nbd->queue_head))
> >                 return;
> > -
> > -       spin_lock_irqsave(&nbd->sock_lock, flags);
> > -
> >         nbd->timedout = true;
> > -
> > -       if (nbd->sock)
> > -               kernel_sock_shutdown(nbd->sock, SHUT_RDWR);
> > -
> > -       spin_unlock_irqrestore(&nbd->sock_lock, flags);
> > -
> > +       schedule_work(&nbd->ws_shutdown);
> > +       /*
> > +        * Make sure sender thread sees nbd->timedout.
> > +        */
> > +       smp_wmb();
> > +       wake_up(&nbd->waiting_wq);
> >         dev_err(nbd_to_dev(nbd), "Connection timed out, shutting down connection\n");
> >  }
> >
> > @@ -592,7 +598,11 @@ static int nbd_thread_send(void *data)
> >                 spin_unlock_irq(&nbd->queue_lock);
> >
> >                 /* handle request */
> > -               nbd_handle_req(nbd, req);
> > +               if (nbd->timedout) {
> > +                       req->errors++;
> > +                       nbd_end_request(nbd, req);
> > +               } else
> > +                       nbd_handle_req(nbd, req);
> >         }
> >
> >         nbd->task_send = NULL;
> > @@ -672,6 +682,7 @@ static void nbd_reset(struct nbd_device *nbd)
> >         set_capacity(nbd->disk, 0);
> >         nbd->flags = 0;
> >         nbd->xmit_timeout = 0;
> > +       INIT_WORK(&nbd->ws_shutdown, nbd_ws_func_shutdown);
> >         queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
> >         del_timer_sync(&nbd->timeout_timer);
> >  }
> > @@ -804,15 +815,15 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
> >                 nbd_dev_dbg_close(nbd);
> >                 kthread_stop(thread);
> >
> > -               mutex_lock(&nbd->tx_lock);
> > -
> >                 sock_shutdown(nbd);
> > +               mutex_lock(&nbd->tx_lock);
> >                 nbd_clear_que(nbd);
> >                 kill_bdev(bdev);
> >                 nbd_bdev_reset(bdev);
> >
> >                 if (nbd->disconnect) /* user requested, ignore socket errors */
> >                         error = 0;
> > +
> >                 if (nbd->timedout)
> >                         error = -ETIMEDOUT;
> >
> > @@ -863,6 +874,14 @@ static const struct block_device_operations nbd_fops =
> >         .compat_ioctl = nbd_ioctl,
> >  };
> >
> > +static void nbd_ws_func_shutdown(struct work_struct *ws_nbd)
> > +{
> > +       struct nbd_device *nbd_dev = container_of(ws_nbd, struct nbd_device,
> > +                                                       ws_shutdown);
> > +
> > +       sock_shutdown(nbd_dev);
> > +}
> > +
> >  #if IS_ENABLED(CONFIG_DEBUG_FS)
> >
> >  static int nbd_dbg_tasks_show(struct seq_file *s, void *unused)
> > --
> > 2.6.2
> >
>
>
> Any update for the above patch series?
> --
>         ---P.K.S

ping??



-- 
        ---P.K.S