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Commit a46b5367 authored by Juergen Gross's avatar Juergen Gross Committed by Konrad Rzeszutek Wilk
Browse files

xen/blkfront: cleanup stale persistent grants 



Add a periodic cleanup function to remove old persistent grants which
are no longer in use on the backend side. This avoids starvation in
case there are lots of persistent grants for a device which no longer
is involved in I/O business.

Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Reviewed-by: default avatarRoger Pau Monné <roger.pau@citrix.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 973e5405

drivers/block/xen-blkfront.c

+90 −4
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ 
#include <linux/scatterlist.h>

#include <linux/bitmap.h>

#include <linux/list.h>

#include <linux/workqueue.h>



#include <xen/xen.h>

#include <xen/xenbus.h>
@@ -121,6 +122,8 @@ static inline struct blkif_req *blkif_req(struct request *rq) 


static DEFINE_MUTEX(blkfront_mutex);

static const struct block_device_operations xlvbd_block_fops;

static struct delayed_work blkfront_work;

static LIST_HEAD(info_list);



/*

 * Maximum number of segments in indirect requests, the actual value used by
@@ -216,6 +219,7 @@ struct blkfront_info 
	/* Save uncomplete reqs and bios for migration. */

	struct list_head requests;

	struct bio_list bio_list;

	struct list_head info_list;

};



static unsigned int nr_minors;
@@ -1759,6 +1763,12 @@ static int write_per_ring_nodes(struct xenbus_transaction xbt, 
	return err;

}



static void free_info(struct blkfront_info *info)

{

	list_del(&info->info_list);

	kfree(info);

}



/* Common code used when first setting up, and when resuming. */

static int talk_to_blkback(struct xenbus_device *dev,

			   struct blkfront_info *info)
@@ -1880,7 +1890,10 @@ static int talk_to_blkback(struct xenbus_device *dev, 
 destroy_blkring:

	blkif_free(info, 0);



	kfree(info);

	mutex_lock(&blkfront_mutex);

	free_info(info);

	mutex_unlock(&blkfront_mutex);



	dev_set_drvdata(&dev->dev, NULL);



	return err;
@@ -1991,6 +2004,10 @@ static int blkfront_probe(struct xenbus_device *dev, 
	info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0);

	dev_set_drvdata(&dev->dev, info);



	mutex_lock(&blkfront_mutex);

	list_add(&info->info_list, &info_list);

	mutex_unlock(&blkfront_mutex);



	return 0;

}
@@ -2301,6 +2318,12 @@ static void blkfront_gather_backend_features(struct blkfront_info *info) 
	if (indirect_segments <= BLKIF_MAX_SEGMENTS_PER_REQUEST)

		indirect_segments = 0;

	info->max_indirect_segments = indirect_segments;



	if (info->feature_persistent) {

		mutex_lock(&blkfront_mutex);

		schedule_delayed_work(&blkfront_work, HZ * 10);

		mutex_unlock(&blkfront_mutex);

	}

}



/*
@@ -2482,7 +2505,9 @@ static int blkfront_remove(struct xenbus_device *xbdev) 
	mutex_unlock(&info->mutex);



	if (!bdev) {

		kfree(info);

		mutex_lock(&blkfront_mutex);

		free_info(info);

		mutex_unlock(&blkfront_mutex);

		return 0;

	}
@@ -2502,7 +2527,9 @@ static int blkfront_remove(struct xenbus_device *xbdev) 
	if (info && !bdev->bd_openers) {

		xlvbd_release_gendisk(info);

		disk->private_data = NULL;

		kfree(info);

		mutex_lock(&blkfront_mutex);

		free_info(info);

		mutex_unlock(&blkfront_mutex);

	}



	mutex_unlock(&bdev->bd_mutex);
@@ -2585,7 +2612,7 @@ static void blkif_release(struct gendisk *disk, fmode_t mode) 
		dev_info(disk_to_dev(bdev->bd_disk), "releasing disk\n");

		xlvbd_release_gendisk(info);

		disk->private_data = NULL;

		kfree(info);

		free_info(info);

	}



out:
@@ -2618,6 +2645,61 @@ static struct xenbus_driver blkfront_driver = { 
	.is_ready = blkfront_is_ready,

};



static void purge_persistent_grants(struct blkfront_info *info)

{

	unsigned int i;

	unsigned long flags;



	for (i = 0; i < info->nr_rings; i++) {

		struct blkfront_ring_info *rinfo = &info->rinfo[i];

		struct grant *gnt_list_entry, *tmp;



		spin_lock_irqsave(&rinfo->ring_lock, flags);



		if (rinfo->persistent_gnts_c == 0) {

			spin_unlock_irqrestore(&rinfo->ring_lock, flags);

			continue;

		}



		list_for_each_entry_safe(gnt_list_entry, tmp, &rinfo->grants,

					 node) {

			if (gnt_list_entry->gref == GRANT_INVALID_REF ||

			    gnttab_query_foreign_access(gnt_list_entry->gref))

				continue;



			list_del(&gnt_list_entry->node);

			gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL);

			rinfo->persistent_gnts_c--;

			__free_page(gnt_list_entry->page);

			kfree(gnt_list_entry);

		}



		spin_unlock_irqrestore(&rinfo->ring_lock, flags);

	}

}



static void blkfront_delay_work(struct work_struct *work)

{

	struct blkfront_info *info;

	bool need_schedule_work = false;



	mutex_lock(&blkfront_mutex);



	list_for_each_entry(info, &info_list, info_list) {

		if (info->feature_persistent) {

			need_schedule_work = true;

			mutex_lock(&info->mutex);

			purge_persistent_grants(info);

			mutex_unlock(&info->mutex);

		}

	}



	if (need_schedule_work)

		schedule_delayed_work(&blkfront_work, HZ * 10);



	mutex_unlock(&blkfront_mutex);

}



static int __init xlblk_init(void)

{

	int ret;
@@ -2650,6 +2732,8 @@ static int __init xlblk_init(void) 
		return -ENODEV;

	}



	INIT_DELAYED_WORK(&blkfront_work, blkfront_delay_work);



	ret = xenbus_register_frontend(&blkfront_driver);

	if (ret) {

		unregister_blkdev(XENVBD_MAJOR, DEV_NAME);
@@ -2663,6 +2747,8 @@ module_init(xlblk_init); 


static void __exit xlblk_exit(void)

{

	cancel_delayed_work_sync(&blkfront_work);



	xenbus_unregister_driver(&blkfront_driver);

	unregister_blkdev(XENVBD_MAJOR, DEV_NAME);

	kfree(minors);