diff mbox series

[06/12] xen-blkfront: add callbacks for PM suspend and hibernation

Message ID ad580b4d5b76c18fe2fe409704f25622e01af361.1589926004.git.anchalag@amazon.com (mailing list archive)
State Superseded
Headers show
Series Fix PM hibernation in Xen guests | expand

Commit Message

Anchal Agarwal May 19, 2020, 11:27 p.m. UTC 
From: Munehisa Kamata <kamatam@amazon.com>

S4 power transition states are much different than xen
suspend/resume. Former is visible to the guest and frontend drivers should
be aware of the state transitions and should be able to take appropriate
actions when needed. In transition to S4 we need to make sure that at least
all the in-flight blkif requests get completed, since they probably contain
bits of the guest's memory image and that's not going to get saved any
other way. Hence, re-issuing of in-flight requests as in case of xen resume
will not work here. This is in contrast to xen-suspend where we need to
freeze with as little processing as possible to avoid dirtying RAM late in
the migration cycle and we know that in-flight data can wait.

Add freeze, thaw and restore callbacks for PM suspend and hibernation
support. All frontend drivers that needs to use PM_HIBERNATION/PM_SUSPEND
events, need to implement these xenbus_driver callbacks. The freeze handler
stops block-layer queue and disconnect the frontend from the backend while
freeing ring_info and associated resources. Before disconnecting from the
backend, we need to prevent any new IO from being queued and wait for existing
IO to complete. Freeze/unfreeze of the queues will guarantee that there are no
requests in use on the shared ring. However, for sanity we should check
state of the ring before disconnecting to make sure that there are no
outstanding requests to be processed on the ring. The restore handler
re-allocates ring_info, unquiesces and unfreezes the queue and re-connect to
the backend, so that rest of the kernel can continue to use the block device
transparently.

Note:For older backends,if a backend doesn't have commit'12ea729645ace'
xen/blkback: unmap all persistent grants when frontend gets disconnected,
the frontend may see massive amount of grant table warning when freeing
resources.
[   36.852659] deferring g.e. 0xf9 (pfn 0xffffffffffffffff)
[   36.855089] xen:grant_table: WARNING:e.g. 0x112 still in use!

In this case, persistent grants would need to be disabled.

[Anchal Changelog: Removed timeout/request during blkfront freeze.
Reworked the whole patch to work with blk-mq and incorporate upstream's
comments]

Signed-off-by: Anchal Agarwal <anchalag@amazon.com>
Signed-off-by: Munehisa Kamata <kamatam@amazon.com>
---
 drivers/block/xen-blkfront.c | 122 +++++++++++++++++++++++++++++++++--
 1 file changed, 115 insertions(+), 7 deletions(-)

Comments

kernel test robot May 20, 2020, 5 a.m. UTC | #1 
Hi Anchal,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.7-rc6]
[cannot apply to xen-tip/linux-next tip/irq/core tip/auto-latest next-20200519]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Anchal-Agarwal/Fix-PM-hibernation-in-Xen-guests/20200520-073211
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 03fb3acae4be8a6b680ffedb220a8b6c07260b40
config: x86_64-randconfig-a016-20200519 (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project e6658079aca6d971b4e9d7137a3a2ecbc9c34aec)
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All error/warnings (new ones prefixed by >>, old ones prefixed by <<):

>> drivers/block/xen-blkfront.c:2699:30: warning: missing terminating '"' character [-Winvalid-pp-token]
xenbus_dev_error(dev, err, "Hibernation Failed.
^
>> drivers/block/xen-blkfront.c:2699:30: error: expected expression
drivers/block/xen-blkfront.c:2700:26: warning: missing terminating '"' character [-Winvalid-pp-token]
The ring is still busy");
^
>> drivers/block/xen-blkfront.c:2726:1: error: function definition is not allowed here
{
^
>> drivers/block/xen-blkfront.c:2762:10: error: use of undeclared identifier 'blkfront_restore'
.thaw = blkfront_restore,
^
drivers/block/xen-blkfront.c:2763:13: error: use of undeclared identifier 'blkfront_restore'
.restore = blkfront_restore
^
drivers/block/xen-blkfront.c:2767:1: error: function definition is not allowed here
{
^
drivers/block/xen-blkfront.c:2800:1: error: function definition is not allowed here
{
^
drivers/block/xen-blkfront.c:2822:1: error: function definition is not allowed here
{
^
>> drivers/block/xen-blkfront.c:2863:13: error: use of undeclared identifier 'xlblk_init'
module_init(xlblk_init);
^
drivers/block/xen-blkfront.c:2867:1: error: function definition is not allowed here
{
^
>> drivers/block/xen-blkfront.c:2874:13: error: use of undeclared identifier 'xlblk_exit'
module_exit(xlblk_exit);
^
>> drivers/block/xen-blkfront.c:2880:24: error: expected '}'
MODULE_ALIAS("xenblk");
^
drivers/block/xen-blkfront.c:2674:1: note: to match this '{'
{
^
>> drivers/block/xen-blkfront.c:2738:45: warning: ISO C90 forbids mixing declarations and code [-Wdeclaration-after-statement]
static const struct block_device_operations xlvbd_block_fops =
^
3 warnings and 11 errors generated.

vim +2699 drivers/block/xen-blkfront.c

  2672	
  2673	static int blkfront_freeze(struct xenbus_device *dev)
  2674	{
  2675		unsigned int i;
  2676		struct blkfront_info *info = dev_get_drvdata(&dev->dev);
  2677		struct blkfront_ring_info *rinfo;
  2678		/* This would be reasonable timeout as used in xenbus_dev_shutdown() */
  2679		unsigned int timeout = 5 * HZ;
  2680		unsigned long flags;
  2681		int err = 0;
  2682	
  2683		info->connected = BLKIF_STATE_FREEZING;
  2684	
  2685		blk_mq_freeze_queue(info->rq);
  2686		blk_mq_quiesce_queue(info->rq);
  2687	
  2688		for_each_rinfo(info, rinfo, i) {
  2689		    /* No more gnttab callback work. */
  2690		    gnttab_cancel_free_callback(&rinfo->callback);
  2691		    /* Flush gnttab callback work. Must be done with no locks held. */
  2692		    flush_work(&rinfo->work);
  2693		}
  2694	
  2695		for_each_rinfo(info, rinfo, i) {
  2696		    spin_lock_irqsave(&rinfo->ring_lock, flags);
  2697		    if (RING_FULL(&rinfo->ring)
  2698			    || RING_HAS_UNCONSUMED_RESPONSES(&rinfo->ring)) {
> 2699			xenbus_dev_error(dev, err, "Hibernation Failed.
  2700				The ring is still busy");
  2701			info->connected = BLKIF_STATE_CONNECTED;
  2702			spin_unlock_irqrestore(&rinfo->ring_lock, flags);
  2703			return -EBUSY;
  2704		}
  2705		    spin_unlock_irqrestore(&rinfo->ring_lock, flags);
  2706		}
  2707		/* Kick the backend to disconnect */
  2708		xenbus_switch_state(dev, XenbusStateClosing);
  2709	
  2710		/*
  2711		 * We don't want to move forward before the frontend is diconnected
  2712		 * from the backend cleanly.
  2713		 */
  2714		timeout = wait_for_completion_timeout(&info->wait_backend_disconnected,
  2715						      timeout);
  2716		if (!timeout) {
  2717			err = -EBUSY;
  2718			xenbus_dev_error(dev, err, "Freezing timed out;"
  2719					 "the device may become inconsistent state");
  2720		}
  2721	
  2722		return err;
  2723	}
  2724	
  2725	static int blkfront_restore(struct xenbus_device *dev)
> 2726	{
  2727		struct blkfront_info *info = dev_get_drvdata(&dev->dev);
  2728		int err = 0;
  2729	
  2730		err = talk_to_blkback(dev, info);
  2731		blk_mq_unquiesce_queue(info->rq);
  2732		blk_mq_unfreeze_queue(info->rq);
  2733		if (!err)
  2734		    blk_mq_update_nr_hw_queues(&info->tag_set, info->nr_rings);
  2735		return err;
  2736	}
  2737	
> 2738	static const struct block_device_operations xlvbd_block_fops =
  2739	{
  2740		.owner = THIS_MODULE,
  2741		.open = blkif_open,
  2742		.release = blkif_release,
  2743		.getgeo = blkif_getgeo,
  2744		.ioctl = blkif_ioctl,
  2745		.compat_ioctl = blkdev_compat_ptr_ioctl,
  2746	};
  2747	
  2748	
  2749	static const struct xenbus_device_id blkfront_ids[] = {
  2750		{ "vbd" },
  2751		{ "" }
  2752	};
  2753	
  2754	static struct xenbus_driver blkfront_driver = {
  2755		.ids  = blkfront_ids,
  2756		.probe = blkfront_probe,
  2757		.remove = blkfront_remove,
  2758		.resume = blkfront_resume,
  2759		.otherend_changed = blkback_changed,
  2760		.is_ready = blkfront_is_ready,
  2761		.freeze = blkfront_freeze,
> 2762		.thaw = blkfront_restore,
  2763		.restore = blkfront_restore
  2764	};
  2765	
  2766	static void purge_persistent_grants(struct blkfront_info *info)
> 2767	{
  2768		unsigned int i;
  2769		unsigned long flags;
  2770		struct blkfront_ring_info *rinfo;
  2771	
  2772		for_each_rinfo(info, rinfo, i) {
  2773			struct grant *gnt_list_entry, *tmp;
  2774	
  2775			spin_lock_irqsave(&rinfo->ring_lock, flags);
  2776	
  2777			if (rinfo->persistent_gnts_c == 0) {
  2778				spin_unlock_irqrestore(&rinfo->ring_lock, flags);
  2779				continue;
  2780			}
  2781	
  2782			list_for_each_entry_safe(gnt_list_entry, tmp, &rinfo->grants,
  2783						 node) {
  2784				if (gnt_list_entry->gref == GRANT_INVALID_REF ||
  2785				    gnttab_query_foreign_access(gnt_list_entry->gref))
  2786					continue;
  2787	
  2788				list_del(&gnt_list_entry->node);
  2789				gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL);
  2790				rinfo->persistent_gnts_c--;
  2791				gnt_list_entry->gref = GRANT_INVALID_REF;
  2792				list_add_tail(&gnt_list_entry->node, &rinfo->grants);
  2793			}
  2794	
  2795			spin_unlock_irqrestore(&rinfo->ring_lock, flags);
  2796		}
  2797	}
  2798	
  2799	static void blkfront_delay_work(struct work_struct *work)
  2800	{
  2801		struct blkfront_info *info;
  2802		bool need_schedule_work = false;
  2803	
  2804		mutex_lock(&blkfront_mutex);
  2805	
  2806		list_for_each_entry(info, &info_list, info_list) {
  2807			if (info->feature_persistent) {
  2808				need_schedule_work = true;
  2809				mutex_lock(&info->mutex);
  2810				purge_persistent_grants(info);
  2811				mutex_unlock(&info->mutex);
  2812			}
  2813		}
  2814	
  2815		if (need_schedule_work)
  2816			schedule_delayed_work(&blkfront_work, HZ * 10);
  2817	
  2818		mutex_unlock(&blkfront_mutex);
  2819	}
  2820	
  2821	static int __init xlblk_init(void)
> 2822	{
  2823		int ret;
  2824		int nr_cpus = num_online_cpus();
  2825	
  2826		if (!xen_domain())
  2827			return -ENODEV;
  2828	
  2829		if (!xen_has_pv_disk_devices())
  2830			return -ENODEV;
  2831	
  2832		if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) {
  2833			pr_warn("xen_blk: can't get major %d with name %s\n",
  2834				XENVBD_MAJOR, DEV_NAME);
  2835			return -ENODEV;
  2836		}
  2837	
  2838		if (xen_blkif_max_segments < BLKIF_MAX_SEGMENTS_PER_REQUEST)
  2839			xen_blkif_max_segments = BLKIF_MAX_SEGMENTS_PER_REQUEST;
  2840	
  2841		if (xen_blkif_max_ring_order > XENBUS_MAX_RING_GRANT_ORDER) {
  2842			pr_info("Invalid max_ring_order (%d), will use default max: %d.\n",
  2843				xen_blkif_max_ring_order, XENBUS_MAX_RING_GRANT_ORDER);
  2844			xen_blkif_max_ring_order = XENBUS_MAX_RING_GRANT_ORDER;
  2845		}
  2846	
  2847		if (xen_blkif_max_queues > nr_cpus) {
  2848			pr_info("Invalid max_queues (%d), will use default max: %d.\n",
  2849				xen_blkif_max_queues, nr_cpus);
  2850			xen_blkif_max_queues = nr_cpus;
  2851		}
  2852	
  2853		INIT_DELAYED_WORK(&blkfront_work, blkfront_delay_work);
  2854	
  2855		ret = xenbus_register_frontend(&blkfront_driver);
  2856		if (ret) {
  2857			unregister_blkdev(XENVBD_MAJOR, DEV_NAME);
  2858			return ret;
  2859		}
  2860	
  2861		return 0;
  2862	}
> 2863	module_init(xlblk_init);
  2864	
  2865	
  2866	static void __exit xlblk_exit(void)
  2867	{
  2868		cancel_delayed_work_sync(&blkfront_work);
  2869	
  2870		xenbus_unregister_driver(&blkfront_driver);
  2871		unregister_blkdev(XENVBD_MAJOR, DEV_NAME);
  2872		kfree(minors);
  2873	}
> 2874	module_exit(xlblk_exit);
  2875	
  2876	MODULE_DESCRIPTION("Xen virtual block device frontend");
  2877	MODULE_LICENSE("GPL");
  2878	MODULE_ALIAS_BLOCKDEV_MAJOR(XENVBD_MAJOR);
  2879	MODULE_ALIAS("xen:vbd");
> 2880	MODULE_ALIAS("xenblk");

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
kernel test robot May 20, 2020, 5:07 a.m. UTC | #2 
Hi Anchal,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.7-rc6]
[cannot apply to xen-tip/linux-next tip/irq/core tip/auto-latest next-20200519]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Anchal-Agarwal/Fix-PM-hibernation-in-Xen-guests/20200520-073211
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 03fb3acae4be8a6b680ffedb220a8b6c07260b40
config: x86_64-rhel (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All error/warnings (new ones prefixed by >>, old ones prefixed by <<):

drivers/block/xen-blkfront.c: In function 'blkfront_freeze':
>> drivers/block/xen-blkfront.c:2699:30: warning: missing terminating " character
xenbus_dev_error(dev, err, "Hibernation Failed.
^
>> drivers/block/xen-blkfront.c:2699:30: error: missing terminating " character
xenbus_dev_error(dev, err, "Hibernation Failed.
^~~~~~~~~~~~~~~~~~~~
>> drivers/block/xen-blkfront.c:2700:4: error: 'The' undeclared (first use in this function)
The ring is still busy");
^~~
drivers/block/xen-blkfront.c:2700:4: note: each undeclared identifier is reported only once for each function it appears in
>> drivers/block/xen-blkfront.c:2700:8: error: expected ')' before 'ring'
The ring is still busy");
^~~~
drivers/block/xen-blkfront.c:2700:26: warning: missing terminating " character
The ring is still busy");
^
drivers/block/xen-blkfront.c:2700:26: error: missing terminating " character
The ring is still busy");
^~~
>> drivers/block/xen-blkfront.c:2704:2: error: expected ';' before '}' token
}
^

vim +2699 drivers/block/xen-blkfront.c

  2672	
  2673	static int blkfront_freeze(struct xenbus_device *dev)
  2674	{
  2675		unsigned int i;
  2676		struct blkfront_info *info = dev_get_drvdata(&dev->dev);
  2677		struct blkfront_ring_info *rinfo;
  2678		/* This would be reasonable timeout as used in xenbus_dev_shutdown() */
  2679		unsigned int timeout = 5 * HZ;
  2680		unsigned long flags;
  2681		int err = 0;
  2682	
  2683		info->connected = BLKIF_STATE_FREEZING;
  2684	
  2685		blk_mq_freeze_queue(info->rq);
  2686		blk_mq_quiesce_queue(info->rq);
  2687	
  2688		for_each_rinfo(info, rinfo, i) {
  2689		    /* No more gnttab callback work. */
  2690		    gnttab_cancel_free_callback(&rinfo->callback);
  2691		    /* Flush gnttab callback work. Must be done with no locks held. */
  2692		    flush_work(&rinfo->work);
  2693		}
  2694	
  2695		for_each_rinfo(info, rinfo, i) {
  2696		    spin_lock_irqsave(&rinfo->ring_lock, flags);
  2697		    if (RING_FULL(&rinfo->ring)
  2698			    || RING_HAS_UNCONSUMED_RESPONSES(&rinfo->ring)) {
> 2699			xenbus_dev_error(dev, err, "Hibernation Failed.
> 2700				The ring is still busy");
  2701			info->connected = BLKIF_STATE_CONNECTED;
  2702			spin_unlock_irqrestore(&rinfo->ring_lock, flags);
  2703			return -EBUSY;
> 2704		}
  2705		    spin_unlock_irqrestore(&rinfo->ring_lock, flags);
  2706		}
  2707		/* Kick the backend to disconnect */
  2708		xenbus_switch_state(dev, XenbusStateClosing);
  2709	
  2710		/*
  2711		 * We don't want to move forward before the frontend is diconnected
  2712		 * from the backend cleanly.
  2713		 */
  2714		timeout = wait_for_completion_timeout(&info->wait_backend_disconnected,
  2715						      timeout);
  2716		if (!timeout) {
  2717			err = -EBUSY;
  2718			xenbus_dev_error(dev, err, "Freezing timed out;"
  2719					 "the device may become inconsistent state");
  2720		}
  2721	
  2722		return err;
  2723	}
  2724	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
kernel test robot May 23, 2020, 12:32 p.m. UTC | #3 
Hi Anchal,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v5.7-rc6]
[cannot apply to xen-tip/linux-next tip/irq/core tip/auto-latest next-20200519]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Anchal-Agarwal/Fix-PM-hibernation-in-Xen-guests/20200520-073211
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 03fb3acae4be8a6b680ffedb220a8b6c07260b40
config: x86_64-allmodconfig (attached as .config)
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.1-193-gb8fad4bc-dirty
        # save the attached .config to linux build tree
        make C=1 ARCH=x86_64 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'
:::::: branch date: 11 hours ago
:::::: commit date: 11 hours ago

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>


sparse warnings: (new ones prefixed by >>)

>> drivers/block/xen-blkfront.c:2700:0: sparse: sparse: missing terminating " character
   drivers/block/xen-blkfront.c:2701:0: sparse: sparse: missing terminating " character
   drivers/block/xen-blkfront.c:2700:25: sparse: sparse: Expected ) in function call
   drivers/block/xen-blkfront.c:2700:25: sparse: sparse: got The

# https://github.com/0day-ci/linux/commit/1997467d18e784a64ee0fe00875492e9605f6147
git remote add linux-review https://github.com/0day-ci/linux
git remote update linux-review
git checkout 1997467d18e784a64ee0fe00875492e9605f6147
vim +2700 drivers/block/xen-blkfront.c

9f27ee59503865 Jeremy Fitzhardinge 2007-07-17  2672  
1997467d18e784 Munehisa Kamata     2020-05-19  2673  static int blkfront_freeze(struct xenbus_device *dev)
1997467d18e784 Munehisa Kamata     2020-05-19  2674  {
1997467d18e784 Munehisa Kamata     2020-05-19  2675  	unsigned int i;
1997467d18e784 Munehisa Kamata     2020-05-19  2676  	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
1997467d18e784 Munehisa Kamata     2020-05-19  2677  	struct blkfront_ring_info *rinfo;
1997467d18e784 Munehisa Kamata     2020-05-19  2678  	/* This would be reasonable timeout as used in xenbus_dev_shutdown() */
1997467d18e784 Munehisa Kamata     2020-05-19  2679  	unsigned int timeout = 5 * HZ;
1997467d18e784 Munehisa Kamata     2020-05-19  2680  	unsigned long flags;
1997467d18e784 Munehisa Kamata     2020-05-19  2681  	int err = 0;
1997467d18e784 Munehisa Kamata     2020-05-19  2682  
1997467d18e784 Munehisa Kamata     2020-05-19  2683  	info->connected = BLKIF_STATE_FREEZING;
1997467d18e784 Munehisa Kamata     2020-05-19  2684  
1997467d18e784 Munehisa Kamata     2020-05-19  2685  	blk_mq_freeze_queue(info->rq);
1997467d18e784 Munehisa Kamata     2020-05-19  2686  	blk_mq_quiesce_queue(info->rq);
1997467d18e784 Munehisa Kamata     2020-05-19  2687  
1997467d18e784 Munehisa Kamata     2020-05-19  2688  	for_each_rinfo(info, rinfo, i) {
1997467d18e784 Munehisa Kamata     2020-05-19  2689  	    /* No more gnttab callback work. */
1997467d18e784 Munehisa Kamata     2020-05-19  2690  	    gnttab_cancel_free_callback(&rinfo->callback);
1997467d18e784 Munehisa Kamata     2020-05-19  2691  	    /* Flush gnttab callback work. Must be done with no locks held. */
1997467d18e784 Munehisa Kamata     2020-05-19  2692  	    flush_work(&rinfo->work);
1997467d18e784 Munehisa Kamata     2020-05-19  2693  	}
1997467d18e784 Munehisa Kamata     2020-05-19  2694  
1997467d18e784 Munehisa Kamata     2020-05-19  2695  	for_each_rinfo(info, rinfo, i) {
1997467d18e784 Munehisa Kamata     2020-05-19  2696  	    spin_lock_irqsave(&rinfo->ring_lock, flags);
1997467d18e784 Munehisa Kamata     2020-05-19  2697  	    if (RING_FULL(&rinfo->ring)
1997467d18e784 Munehisa Kamata     2020-05-19  2698  		    || RING_HAS_UNCONSUMED_RESPONSES(&rinfo->ring)) {
1997467d18e784 Munehisa Kamata     2020-05-19  2699  		xenbus_dev_error(dev, err, "Hibernation Failed.
1997467d18e784 Munehisa Kamata     2020-05-19 @2700  			The ring is still busy");
1997467d18e784 Munehisa Kamata     2020-05-19  2701  		info->connected = BLKIF_STATE_CONNECTED;
1997467d18e784 Munehisa Kamata     2020-05-19  2702  		spin_unlock_irqrestore(&rinfo->ring_lock, flags);
1997467d18e784 Munehisa Kamata     2020-05-19  2703  		return -EBUSY;
1997467d18e784 Munehisa Kamata     2020-05-19  2704  	}
1997467d18e784 Munehisa Kamata     2020-05-19  2705  	    spin_unlock_irqrestore(&rinfo->ring_lock, flags);
1997467d18e784 Munehisa Kamata     2020-05-19  2706  	}
1997467d18e784 Munehisa Kamata     2020-05-19  2707  	/* Kick the backend to disconnect */
1997467d18e784 Munehisa Kamata     2020-05-19  2708  	xenbus_switch_state(dev, XenbusStateClosing);
1997467d18e784 Munehisa Kamata     2020-05-19  2709  
1997467d18e784 Munehisa Kamata     2020-05-19  2710  	/*
1997467d18e784 Munehisa Kamata     2020-05-19  2711  	 * We don't want to move forward before the frontend is diconnected
1997467d18e784 Munehisa Kamata     2020-05-19  2712  	 * from the backend cleanly.
1997467d18e784 Munehisa Kamata     2020-05-19  2713  	 */
1997467d18e784 Munehisa Kamata     2020-05-19  2714  	timeout = wait_for_completion_timeout(&info->wait_backend_disconnected,
1997467d18e784 Munehisa Kamata     2020-05-19  2715  					      timeout);
1997467d18e784 Munehisa Kamata     2020-05-19  2716  	if (!timeout) {
1997467d18e784 Munehisa Kamata     2020-05-19  2717  		err = -EBUSY;
1997467d18e784 Munehisa Kamata     2020-05-19  2718  		xenbus_dev_error(dev, err, "Freezing timed out;"
1997467d18e784 Munehisa Kamata     2020-05-19  2719  				 "the device may become inconsistent state");
1997467d18e784 Munehisa Kamata     2020-05-19  2720  	}
1997467d18e784 Munehisa Kamata     2020-05-19  2721  
1997467d18e784 Munehisa Kamata     2020-05-19  2722  	return err;
1997467d18e784 Munehisa Kamata     2020-05-19  2723  }
1997467d18e784 Munehisa Kamata     2020-05-19  2724  

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Roger Pau Monné May 28, 2020, 12:30 p.m. UTC | #4 
On Tue, May 19, 2020 at 11:27:50PM +0000, Anchal Agarwal wrote:
> From: Munehisa Kamata <kamatam@amazon.com>
> 
> S4 power transition states are much different than xen
> suspend/resume. Former is visible to the guest and frontend drivers should
> be aware of the state transitions and should be able to take appropriate
> actions when needed. In transition to S4 we need to make sure that at least
> all the in-flight blkif requests get completed, since they probably contain
> bits of the guest's memory image and that's not going to get saved any
> other way. Hence, re-issuing of in-flight requests as in case of xen resume
> will not work here. This is in contrast to xen-suspend where we need to
> freeze with as little processing as possible to avoid dirtying RAM late in
> the migration cycle and we know that in-flight data can wait.
> 
> Add freeze, thaw and restore callbacks for PM suspend and hibernation
> support. All frontend drivers that needs to use PM_HIBERNATION/PM_SUSPEND
> events, need to implement these xenbus_driver callbacks. The freeze handler
> stops block-layer queue and disconnect the frontend from the backend while
> freeing ring_info and associated resources. Before disconnecting from the
> backend, we need to prevent any new IO from being queued and wait for existing
> IO to complete. Freeze/unfreeze of the queues will guarantee that there are no
> requests in use on the shared ring. However, for sanity we should check
> state of the ring before disconnecting to make sure that there are no
> outstanding requests to be processed on the ring. The restore handler
> re-allocates ring_info, unquiesces and unfreezes the queue and re-connect to
> the backend, so that rest of the kernel can continue to use the block device
> transparently.
> 
> Note:For older backends,if a backend doesn't have commit'12ea729645ace'
> xen/blkback: unmap all persistent grants when frontend gets disconnected,
> the frontend may see massive amount of grant table warning when freeing
> resources.
> [   36.852659] deferring g.e. 0xf9 (pfn 0xffffffffffffffff)
> [   36.855089] xen:grant_table: WARNING:e.g. 0x112 still in use!
> 
> In this case, persistent grants would need to be disabled.
> 
> [Anchal Changelog: Removed timeout/request during blkfront freeze.
> Reworked the whole patch to work with blk-mq and incorporate upstream's
> comments]

Please tag versions using vX and it would be helpful if you could list
the specific changes that you performed between versions. There where
3 RFC versions IIRC, and there's no log of the changes between them.

> 
> Signed-off-by: Anchal Agarwal <anchalag@amazon.com>
> Signed-off-by: Munehisa Kamata <kamatam@amazon.com>
> ---
>  drivers/block/xen-blkfront.c | 122 +++++++++++++++++++++++++++++++++--
>  1 file changed, 115 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 3b889ea950c2..464863ed7093 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -48,6 +48,8 @@
>  #include <linux/list.h>
>  #include <linux/workqueue.h>
>  #include <linux/sched/mm.h>
> +#include <linux/completion.h>
> +#include <linux/delay.h>
>  
>  #include <xen/xen.h>
>  #include <xen/xenbus.h>
> @@ -80,6 +82,8 @@ enum blkif_state {
>  	BLKIF_STATE_DISCONNECTED,
>  	BLKIF_STATE_CONNECTED,
>  	BLKIF_STATE_SUSPENDED,
> +	BLKIF_STATE_FREEZING,
> +	BLKIF_STATE_FROZEN

Nit: adding a terminating ',' would prevent further additions from
having to modify this line.

>  };
>  
>  struct grant {
> @@ -219,6 +223,7 @@ struct blkfront_info
>  	struct list_head requests;
>  	struct bio_list bio_list;
>  	struct list_head info_list;
> +	struct completion wait_backend_disconnected;
>  };
>  
>  static unsigned int nr_minors;
> @@ -1005,6 +1010,7 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
>  	info->sector_size = sector_size;
>  	info->physical_sector_size = physical_sector_size;
>  	blkif_set_queue_limits(info);
> +	init_completion(&info->wait_backend_disconnected);
>  
>  	return 0;
>  }
> @@ -1057,7 +1063,7 @@ static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
>  		case XEN_SCSI_DISK5_MAJOR:
>  		case XEN_SCSI_DISK6_MAJOR:
>  		case XEN_SCSI_DISK7_MAJOR:
> -			*offset = (*minor / PARTS_PER_DISK) + 
> +			*offset = (*minor / PARTS_PER_DISK) +
>  				((major - XEN_SCSI_DISK1_MAJOR + 1) * 16) +
>  				EMULATED_SD_DISK_NAME_OFFSET;
>  			*minor = *minor +
> @@ -1072,7 +1078,7 @@ static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
>  		case XEN_SCSI_DISK13_MAJOR:
>  		case XEN_SCSI_DISK14_MAJOR:
>  		case XEN_SCSI_DISK15_MAJOR:
> -			*offset = (*minor / PARTS_PER_DISK) + 
> +			*offset = (*minor / PARTS_PER_DISK) +

Unrelated changes, please split to a pre-patch.

>  				((major - XEN_SCSI_DISK8_MAJOR + 8) * 16) +
>  				EMULATED_SD_DISK_NAME_OFFSET;
>  			*minor = *minor +
> @@ -1353,6 +1359,8 @@ static void blkif_free(struct blkfront_info *info, int suspend)
>  	unsigned int i;
>  	struct blkfront_ring_info *rinfo;
>  
> +	if (info->connected == BLKIF_STATE_FREEZING)
> +		goto free_rings;
>  	/* Prevent new requests being issued until we fix things up. */
>  	info->connected = suspend ?
>  		BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
> @@ -1360,6 +1368,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
>  	if (info->rq)
>  		blk_mq_stop_hw_queues(info->rq);
>  
> +free_rings:
>  	for_each_rinfo(info, rinfo, i)
>  		blkif_free_ring(rinfo);
>  
> @@ -1563,8 +1572,10 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
>  	struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)dev_id;
>  	struct blkfront_info *info = rinfo->dev_info;
>  
> -	if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
> -		return IRQ_HANDLED;
> +	if (unlikely(info->connected != BLKIF_STATE_CONNECTED
> +		    && info->connected != BLKIF_STATE_FREEZING)){

Extra tab and missing space between '){'. Also my preference would be
for the && to go at the end of the previous line, like it's done
elsewhere in the file.

> +	    return IRQ_HANDLED;
> +	}
>  
>  	spin_lock_irqsave(&rinfo->ring_lock, flags);
>   again:
> @@ -2027,6 +2038,7 @@ static int blkif_recover(struct blkfront_info *info)
>  	unsigned int segs;
>  	struct blkfront_ring_info *rinfo;
>  
> +	bool frozen = info->connected == BLKIF_STATE_FROZEN;

Please put this together with the rest of the variable definitions,
and leave the empty line as a split between variable definitions and
code. I've already requested this on RFC v3 but you seem to have
dropped some of the requests I've made there.

>  	blkfront_gather_backend_features(info);
>  	/* Reset limits changed by blk_mq_update_nr_hw_queues(). */
>  	blkif_set_queue_limits(info);
> @@ -2048,6 +2060,9 @@ static int blkif_recover(struct blkfront_info *info)
>  		kick_pending_request_queues(rinfo);
>  	}
>  
> +	if (frozen)
> +		return 0;
> +
>  	list_for_each_entry_safe(req, n, &info->requests, queuelist) {
>  		/* Requeue pending requests (flush or discard) */
>  		list_del_init(&req->queuelist);
> @@ -2364,6 +2379,7 @@ static void blkfront_connect(struct blkfront_info *info)
>  
>  		return;
>  	case BLKIF_STATE_SUSPENDED:
> +	case BLKIF_STATE_FROZEN:
>  		/*
>  		 * If we are recovering from suspension, we need to wait
>  		 * for the backend to announce it's features before
> @@ -2481,12 +2497,36 @@ static void blkback_changed(struct xenbus_device *dev,
>  		break;
>  
>  	case XenbusStateClosed:
> -		if (dev->state == XenbusStateClosed)
> +		if (dev->state == XenbusStateClosed) {
> +			if (info->connected == BLKIF_STATE_FREEZING) {
> +				blkif_free(info, 0);
> +				info->connected = BLKIF_STATE_FROZEN;
> +				complete(&info->wait_backend_disconnected);
> +				break;

There's no need for the break here, you can rely on the break below.

> +			}
> +
>  			break;
> +		}
> +
> +		/*
> +		 * We may somehow receive backend's Closed again while thawing
> +		 * or restoring and it causes thawing or restoring to fail.
> +		 * Ignore such unexpected state regardless of the backend state.
> +		 */
> +		if (info->connected == BLKIF_STATE_FROZEN) {

I think you can join this with the previous dev->state == XenbusStateClosed?

Also, won't the device be in the Closed state already if it's in state
frozen?

> +			dev_dbg(&dev->dev,
> +					"ignore the backend's Closed state: %s",
> +					dev->nodename);
> +			break;
> +		}
>  		/* fall through */
>  	case XenbusStateClosing:
> -		if (info)
> -			blkfront_closing(info);
> +		if (info) {
> +			if (info->connected == BLKIF_STATE_FREEZING)
> +				xenbus_frontend_closed(dev);
> +			else
> +				blkfront_closing(info);
> +		}
>  		break;
>  	}
>  }
> @@ -2630,6 +2670,71 @@ static void blkif_release(struct gendisk *disk, fmode_t mode)
>  	mutex_unlock(&blkfront_mutex);
>  }
>  
> +static int blkfront_freeze(struct xenbus_device *dev)
> +{
> +	unsigned int i;
> +	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
> +	struct blkfront_ring_info *rinfo;
> +	/* This would be reasonable timeout as used in xenbus_dev_shutdown() */
> +	unsigned int timeout = 5 * HZ;
> +	unsigned long flags;
> +	int err = 0;
> +
> +	info->connected = BLKIF_STATE_FREEZING;
> +
> +	blk_mq_freeze_queue(info->rq);
> +	blk_mq_quiesce_queue(info->rq);
> +
> +	for_each_rinfo(info, rinfo, i) {
> +	    /* No more gnttab callback work. */
> +	    gnttab_cancel_free_callback(&rinfo->callback);
> +	    /* Flush gnttab callback work. Must be done with no locks held. */
> +	    flush_work(&rinfo->work);
> +	}
> +
> +	for_each_rinfo(info, rinfo, i) {
> +	    spin_lock_irqsave(&rinfo->ring_lock, flags);
> +	    if (RING_FULL(&rinfo->ring)
> +		    || RING_HAS_UNCONSUMED_RESPONSES(&rinfo->ring)) {

'||' should go at the end of the previous line.

> +		xenbus_dev_error(dev, err, "Hibernation Failed.
> +			The ring is still busy");
> +		info->connected = BLKIF_STATE_CONNECTED;
> +		spin_unlock_irqrestore(&rinfo->ring_lock, flags);

You need to unfreeze the queues here, or else the device will be in a
blocked state AFAICT.

> +		return -EBUSY;
> +	}
> +	    spin_unlock_irqrestore(&rinfo->ring_lock, flags);
> +	}

This block has indentation all messed up.

> +	/* Kick the backend to disconnect */
> +	xenbus_switch_state(dev, XenbusStateClosing);
> +
> +	/*
> +	 * We don't want to move forward before the frontend is diconnected
> +	 * from the backend cleanly.
> +	 */
> +	timeout = wait_for_completion_timeout(&info->wait_backend_disconnected,
> +					      timeout);
> +	if (!timeout) {
> +		err = -EBUSY;

Note err is only used here, and I think could just be dropped.

> +		xenbus_dev_error(dev, err, "Freezing timed out;"
> +				 "the device may become inconsistent state");

Leaving the device in this state is quite bad, as it's in a closed
state and with the queues frozen. You should make an attempt to
restore things to a working state.

> +	}
> +
> +	return err;
> +}
> +
> +static int blkfront_restore(struct xenbus_device *dev)
> +{
> +	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
> +	int err = 0;
> +
> +	err = talk_to_blkback(dev, info);
> +	blk_mq_unquiesce_queue(info->rq);
> +	blk_mq_unfreeze_queue(info->rq);
> +	if (!err)
> +	    blk_mq_update_nr_hw_queues(&info->tag_set, info->nr_rings);

Bad indentation. Also shouldn't you first update the queues and then
unfreeze them?

Thanks, Roger.
diff mbox series

Patch

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 3b889ea950c2..464863ed7093 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -48,6 +48,8 @@ 
 #include <linux/list.h>
 #include <linux/workqueue.h>
 #include <linux/sched/mm.h>
+#include <linux/completion.h>
+#include <linux/delay.h>
 
 #include <xen/xen.h>
 #include <xen/xenbus.h>
@@ -80,6 +82,8 @@  enum blkif_state {
 	BLKIF_STATE_DISCONNECTED,
 	BLKIF_STATE_CONNECTED,
 	BLKIF_STATE_SUSPENDED,
+	BLKIF_STATE_FREEZING,
+	BLKIF_STATE_FROZEN
 };
 
 struct grant {
@@ -219,6 +223,7 @@  struct blkfront_info
 	struct list_head requests;
 	struct bio_list bio_list;
 	struct list_head info_list;
+	struct completion wait_backend_disconnected;
 };
 
 static unsigned int nr_minors;
@@ -1005,6 +1010,7 @@  static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
 	info->sector_size = sector_size;
 	info->physical_sector_size = physical_sector_size;
 	blkif_set_queue_limits(info);
+	init_completion(&info->wait_backend_disconnected);
 
 	return 0;
 }
@@ -1057,7 +1063,7 @@  static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
 		case XEN_SCSI_DISK5_MAJOR:
 		case XEN_SCSI_DISK6_MAJOR:
 		case XEN_SCSI_DISK7_MAJOR:
-			*offset = (*minor / PARTS_PER_DISK) + 
+			*offset = (*minor / PARTS_PER_DISK) +
 				((major - XEN_SCSI_DISK1_MAJOR + 1) * 16) +
 				EMULATED_SD_DISK_NAME_OFFSET;
 			*minor = *minor +
@@ -1072,7 +1078,7 @@  static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
 		case XEN_SCSI_DISK13_MAJOR:
 		case XEN_SCSI_DISK14_MAJOR:
 		case XEN_SCSI_DISK15_MAJOR:
-			*offset = (*minor / PARTS_PER_DISK) + 
+			*offset = (*minor / PARTS_PER_DISK) +
 				((major - XEN_SCSI_DISK8_MAJOR + 8) * 16) +
 				EMULATED_SD_DISK_NAME_OFFSET;
 			*minor = *minor +
@@ -1353,6 +1359,8 @@  static void blkif_free(struct blkfront_info *info, int suspend)
 	unsigned int i;
 	struct blkfront_ring_info *rinfo;
 
+	if (info->connected == BLKIF_STATE_FREEZING)
+		goto free_rings;
 	/* Prevent new requests being issued until we fix things up. */
 	info->connected = suspend ?
 		BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
@@ -1360,6 +1368,7 @@  static void blkif_free(struct blkfront_info *info, int suspend)
 	if (info->rq)
 		blk_mq_stop_hw_queues(info->rq);
 
+free_rings:
 	for_each_rinfo(info, rinfo, i)
 		blkif_free_ring(rinfo);
 
@@ -1563,8 +1572,10 @@  static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 	struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)dev_id;
 	struct blkfront_info *info = rinfo->dev_info;
 
-	if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
-		return IRQ_HANDLED;
+	if (unlikely(info->connected != BLKIF_STATE_CONNECTED
+		    && info->connected != BLKIF_STATE_FREEZING)){
+	    return IRQ_HANDLED;
+	}
 
 	spin_lock_irqsave(&rinfo->ring_lock, flags);
  again:
@@ -2027,6 +2038,7 @@  static int blkif_recover(struct blkfront_info *info)
 	unsigned int segs;
 	struct blkfront_ring_info *rinfo;
 
+	bool frozen = info->connected == BLKIF_STATE_FROZEN;
 	blkfront_gather_backend_features(info);
 	/* Reset limits changed by blk_mq_update_nr_hw_queues(). */
 	blkif_set_queue_limits(info);
@@ -2048,6 +2060,9 @@  static int blkif_recover(struct blkfront_info *info)
 		kick_pending_request_queues(rinfo);
 	}
 
+	if (frozen)
+		return 0;
+
 	list_for_each_entry_safe(req, n, &info->requests, queuelist) {
 		/* Requeue pending requests (flush or discard) */
 		list_del_init(&req->queuelist);
@@ -2364,6 +2379,7 @@  static void blkfront_connect(struct blkfront_info *info)
 
 		return;
 	case BLKIF_STATE_SUSPENDED:
+	case BLKIF_STATE_FROZEN:
 		/*
 		 * If we are recovering from suspension, we need to wait
 		 * for the backend to announce it's features before
@@ -2481,12 +2497,36 @@  static void blkback_changed(struct xenbus_device *dev,
 		break;
 
 	case XenbusStateClosed:
-		if (dev->state == XenbusStateClosed)
+		if (dev->state == XenbusStateClosed) {
+			if (info->connected == BLKIF_STATE_FREEZING) {
+				blkif_free(info, 0);
+				info->connected = BLKIF_STATE_FROZEN;
+				complete(&info->wait_backend_disconnected);
+				break;
+			}
+
 			break;
+		}
+
+		/*
+		 * We may somehow receive backend's Closed again while thawing
+		 * or restoring and it causes thawing or restoring to fail.
+		 * Ignore such unexpected state regardless of the backend state.
+		 */
+		if (info->connected == BLKIF_STATE_FROZEN) {
+			dev_dbg(&dev->dev,
+					"ignore the backend's Closed state: %s",
+					dev->nodename);
+			break;
+		}
 		/* fall through */
 	case XenbusStateClosing:
-		if (info)
-			blkfront_closing(info);
+		if (info) {
+			if (info->connected == BLKIF_STATE_FREEZING)
+				xenbus_frontend_closed(dev);
+			else
+				blkfront_closing(info);
+		}
 		break;
 	}
 }
@@ -2630,6 +2670,71 @@  static void blkif_release(struct gendisk *disk, fmode_t mode)
 	mutex_unlock(&blkfront_mutex);
 }
 
+static int blkfront_freeze(struct xenbus_device *dev)
+{
+	unsigned int i;
+	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
+	struct blkfront_ring_info *rinfo;
+	/* This would be reasonable timeout as used in xenbus_dev_shutdown() */
+	unsigned int timeout = 5 * HZ;
+	unsigned long flags;
+	int err = 0;
+
+	info->connected = BLKIF_STATE_FREEZING;
+
+	blk_mq_freeze_queue(info->rq);
+	blk_mq_quiesce_queue(info->rq);
+
+	for_each_rinfo(info, rinfo, i) {
+	    /* No more gnttab callback work. */
+	    gnttab_cancel_free_callback(&rinfo->callback);
+	    /* Flush gnttab callback work. Must be done with no locks held. */
+	    flush_work(&rinfo->work);
+	}
+
+	for_each_rinfo(info, rinfo, i) {
+	    spin_lock_irqsave(&rinfo->ring_lock, flags);
+	    if (RING_FULL(&rinfo->ring)
+		    || RING_HAS_UNCONSUMED_RESPONSES(&rinfo->ring)) {
+		xenbus_dev_error(dev, err, "Hibernation Failed.
+			The ring is still busy");
+		info->connected = BLKIF_STATE_CONNECTED;
+		spin_unlock_irqrestore(&rinfo->ring_lock, flags);
+		return -EBUSY;
+	}
+	    spin_unlock_irqrestore(&rinfo->ring_lock, flags);
+	}
+	/* Kick the backend to disconnect */
+	xenbus_switch_state(dev, XenbusStateClosing);
+
+	/*
+	 * We don't want to move forward before the frontend is diconnected
+	 * from the backend cleanly.
+	 */
+	timeout = wait_for_completion_timeout(&info->wait_backend_disconnected,
+					      timeout);
+	if (!timeout) {
+		err = -EBUSY;
+		xenbus_dev_error(dev, err, "Freezing timed out;"
+				 "the device may become inconsistent state");
+	}
+
+	return err;
+}
+
+static int blkfront_restore(struct xenbus_device *dev)
+{
+	struct blkfront_info *info = dev_get_drvdata(&dev->dev);
+	int err = 0;
+
+	err = talk_to_blkback(dev, info);
+	blk_mq_unquiesce_queue(info->rq);
+	blk_mq_unfreeze_queue(info->rq);
+	if (!err)
+	    blk_mq_update_nr_hw_queues(&info->tag_set, info->nr_rings);
+	return err;
+}
+
 static const struct block_device_operations xlvbd_block_fops =
 {
 	.owner = THIS_MODULE,
@@ -2653,6 +2758,9 @@  static struct xenbus_driver blkfront_driver = {
 	.resume = blkfront_resume,
 	.otherend_changed = blkback_changed,
 	.is_ready = blkfront_is_ready,
+	.freeze = blkfront_freeze,
+	.thaw = blkfront_restore,
+	.restore = blkfront_restore
 };
 
 static void purge_persistent_grants(struct blkfront_info *info)