From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754797AbcE3MGM (ORCPT ); Mon, 30 May 2016 08:06:12 -0400 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:49456 "EHLO metis.ext.4.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754249AbcE3MGK (ORCPT ); Mon, 30 May 2016 08:06:10 -0400 From: Markus Pargmann To: "Pranay Kr. Srivastava" Cc: nbd-general@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] fix might_sleep warning on socket shutdown. Date: Mon, 30 May 2016 14:06:07 +0200 Message-ID: <2182256.8JNtoMu4uL@adelgunde> User-Agent: KMail/4.14.1 (Linux/4.5.0-0.bpo.2-amd64; KDE/4.14.2; x86_64; ; ) In-Reply-To: <1464089188-6155-2-git-send-email-pranjas@gmail.com> References: <1464089188-6155-1-git-send-email-pranjas@gmail.com> <1464089188-6155-2-git-send-email-pranjas@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart4622997.Aebs3Tr9b9"; micalg="pgp-sha256"; protocol="application/pgp-signature" X-SA-Exim-Connect-IP: 2001:67c:670:100:a61f:72ff:fe68:75ba X-SA-Exim-Mail-From: mpa@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --nextPart4622997.Aebs3Tr9b9 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="us-ascii" Hi, On Tuesday 24 May 2016 14:26:25 Pranay Kr. Srivastava 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. >=20 > Reported-by: Mikulas Patocka > Signed-off-by: Markus Pargmann >=20 > Changelog: > Pranay Kr. Srivastava: >=20 > 1) Use spin_lock instead of irq version for sock_shutdown. >=20 > 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 > --- > drivers/block/nbd.c | 62 +++++++++++++++++++++++++++++------------= =2D--------- > 1 file changed, 35 insertions(+), 27 deletions(-) >=20 > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c > index 08afbc7..a5dab48 100644 > --- a/drivers/block/nbd.c > +++ b/drivers/block/nbd.c > @@ -39,6 +39,7 @@ > #include > =20 > #include > +#include > =20 > struct nbd_device { > =09u32 flags; > @@ -57,7 +58,7 @@ struct nbd_device { > =09int blksize; > =09loff_t bytesize; > =09int xmit_timeout; > -=09bool timedout; > +=09atomic_t timedout; Why are you using atomic here? It seems you are just counting the occurences of timeouts with this but never actually use that number.=20= > =09bool disconnect; /* a disconnect has been requested by user */ > =20 > =09struct timer_list timeout_timer; > @@ -69,6 +70,7 @@ struct nbd_device { > #if IS_ENABLED(CONFIG_DEBUG_FS) > =09struct dentry *dbg_dir; > #endif > +=09struct work_struct ws_nbd; Can you rename this so that it is clear that this is a worker struct specifically for the socket shutdown? > }; > =20 > #if IS_ENABLED(CONFIG_DEBUG_FS) > @@ -94,6 +96,7 @@ static int max_part; > * Thanks go to Jens Axboe and Al Viro for their LKML emails explain= ing this! > */ > static DEFINE_SPINLOCK(nbd_lock); > +static void nbd_work_func(struct work_struct *); Same here. nbd_work_func() doesn't give any hint about the real purpose= of the function. > =20 > static inline struct device *nbd_to_dev(struct nbd_device *nbd) > { > @@ -172,39 +175,31 @@ static void nbd_end_request(struct nbd_device *= nbd, struct request *req) > */ > static void sock_shutdown(struct nbd_device *nbd) > { > -=09spin_lock_irq(&nbd->sock_lock); > - > -=09if (!nbd->sock) { > -=09=09spin_unlock_irq(&nbd->sock_lock); > -=09=09return; > -=09} > +=09struct socket *sock; > =20 > -=09dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n"); > -=09kernel_sock_shutdown(nbd->sock, SHUT_RDWR); > -=09sockfd_put(nbd->sock); > +=09spin_lock(&nbd->sock_lock); > +=09sock =3D nbd->sock; > =09nbd->sock =3D NULL; > -=09spin_unlock_irq(&nbd->sock_lock); > +=09spin_unlock(&nbd->sock_lock); > + > +=09if (!sock) > +=09=09return; > =20 > =09del_timer(&nbd->timeout_timer); > +=09dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n"); > +=09kernel_sock_shutdown(sock, SHUT_RDWR); > +=09sockfd_put(sock); > } > =20 > static void nbd_xmit_timeout(unsigned long arg) > { > =09struct nbd_device *nbd =3D (struct nbd_device *)arg; > -=09unsigned long flags; > =20 > =09if (list_empty(&nbd->queue_head)) > =09=09return; > - > -=09spin_lock_irqsave(&nbd->sock_lock, flags); > - > -=09nbd->timedout =3D true; > - > -=09if (nbd->sock) > -=09=09kernel_sock_shutdown(nbd->sock, SHUT_RDWR); > - > -=09spin_unlock_irqrestore(&nbd->sock_lock, flags); > - > +=09atomic_inc(&nbd->timedout); > +=09schedule_work(&nbd->ws_nbd); > +=09wake_up(&nbd->waiting_wq); > =09dev_err(nbd_to_dev(nbd), "Connection timed out, shutting down con= nection\n"); > } > =20 > @@ -592,7 +587,11 @@ static int nbd_thread_send(void *data) > =09=09spin_unlock_irq(&nbd->queue_lock); > =20 > =09=09/* handle request */ > -=09=09nbd_handle_req(nbd, req); > +=09=09if (atomic_read(&nbd->timedout)) { > +=09=09=09req->errors++; > +=09=09=09nbd_end_request(nbd, req); > +=09=09} else > +=09=09=09nbd_handle_req(nbd, req); > =09} > =20 > =09nbd->task_send =3D NULL; > @@ -666,12 +665,13 @@ out: > static void nbd_reset(struct nbd_device *nbd) > { > =09nbd->disconnect =3D false; > -=09nbd->timedout =3D false; > +=09atomic_set(&nbd->timedout, 0); > =09nbd->blksize =3D 1024; > =09nbd->bytesize =3D 0; > =09set_capacity(nbd->disk, 0); > =09nbd->flags =3D 0; > =09nbd->xmit_timeout =3D 0; > +=09INIT_WORK(&nbd->ws_nbd, nbd_work_func); > =09queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue); > =09del_timer_sync(&nbd->timeout_timer); > } > @@ -804,16 +804,16 @@ static int __nbd_ioctl(struct block_device *bde= v, struct nbd_device *nbd, > =09=09nbd_dev_dbg_close(nbd); > =09=09kthread_stop(thread); > =20 > -=09=09mutex_lock(&nbd->tx_lock); > - > =09=09sock_shutdown(nbd); > +=09=09mutex_lock(&nbd->tx_lock); > =09=09nbd_clear_que(nbd); > =09=09kill_bdev(bdev); > =09=09nbd_bdev_reset(bdev); > =20 > =09=09if (nbd->disconnect) /* user requested, ignore socket errors *= / > =09=09=09error =3D 0; > -=09=09if (nbd->timedout) > + > +=09=09if (atomic_read(&nbd->timedout)) > =09=09=09error =3D -ETIMEDOUT; > =20 > =09=09nbd_reset(nbd); > @@ -863,6 +863,14 @@ static const struct block_device_operations nbd_= fops =3D > =09.compat_ioctl =3D=09nbd_ioctl, > }; > =20 > +static void nbd_work_func(struct work_struct *ws_nbd) > +{ > +=09struct nbd_device *nbd_dev =3D container_of(ws_nbd, struct nbd_de= vice, > +=09=09=09=09=09=09=09=09ws_nbd); Please align line breaks on the opening bracket. Best Regards, Markus =2D-=20 Pengutronix e.K. | = | Industrial Linux Solutions | http://www.pengutronix.de/= | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 = | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-555= 5 | --nextPart4622997.Aebs3Tr9b9 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. 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