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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: Juergen Gross <jgross@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
hifive-unleashed-5.1
Juergen Gross 2018-08-13 16:01:11 +02:00 committed by Konrad Rzeszutek Wilk
parent 973e5405f2
commit a46b53672b
1 changed files with 90 additions and 4 deletions
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94
drivers/block/xen-blkfront.c
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@ -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 @@ abort_transaction:
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 @@ again:
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);