From 973e5405f2f67ddbb2bf07b3ffc71908a37fea8e Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Mon, 13 Aug 2018 16:01:10 +0200 Subject: xen/blkback: don't keep persistent grants too long MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Persistent grants are allocated until a threshold per ring is being reached. Those grants won't be freed until the ring is being destroyed meaning there will be resources kept busy which might no longer be used. Instead of freeing only persistent grants until the threshold is reached add a timestamp and remove all persistent grants not having been in use for a minute. Signed-off-by: Juergen Gross Reviewed-by: Roger Pau Monné Signed-off-by: Konrad Rzeszutek Wilk --- drivers/block/xen-blkback/blkback.c | 88 ++++++++++++++++++++----------------- drivers/block/xen-blkback/common.h | 8 +--- 2 files changed, 50 insertions(+), 46 deletions(-) (limited to 'drivers/block') diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index b55b245e8052..9eae7b243f68 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -83,6 +83,18 @@ module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644); MODULE_PARM_DESC(max_persistent_grants, "Maximum number of grants to map persistently"); +/* + * How long a persistent grant is allowed to remain allocated without being in + * use. The time is in seconds, 0 means indefinitely long. + */ + +static unsigned int xen_blkif_pgrant_timeout = 60; +module_param_named(persistent_grant_unused_seconds, xen_blkif_pgrant_timeout, + uint, 0644); +MODULE_PARM_DESC(persistent_grant_unused_seconds, + "Time in seconds an unused persistent grant is allowed to " + "remain allocated. Default is 60, 0 means unlimited."); + /* * Maximum number of rings/queues blkback supports, allow as many queues as there * are CPUs if user has not specified a value. @@ -123,6 +135,13 @@ module_param(log_stats, int, 0644); /* Number of free pages to remove on each call to gnttab_free_pages */ #define NUM_BATCH_FREE_PAGES 10 +static inline bool persistent_gnt_timeout(struct persistent_gnt *persistent_gnt) +{ + return xen_blkif_pgrant_timeout && + (jiffies - persistent_gnt->last_used >= + HZ * xen_blkif_pgrant_timeout); +} + static inline int get_free_page(struct xen_blkif_ring *ring, struct page **page) { unsigned long flags; @@ -278,7 +297,7 @@ static void put_persistent_gnt(struct xen_blkif_ring *ring, { if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags)) pr_alert_ratelimited("freeing a grant already unused\n"); - set_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags); + persistent_gnt->last_used = jiffies; clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags); atomic_dec(&ring->persistent_gnt_in_use); } @@ -371,26 +390,26 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring) struct persistent_gnt *persistent_gnt; struct rb_node *n; unsigned int num_clean, total; - bool scan_used = false, clean_used = false; + bool scan_used = false; struct rb_root *root; - if (ring->persistent_gnt_c < xen_blkif_max_pgrants || - (ring->persistent_gnt_c == xen_blkif_max_pgrants && - !ring->blkif->vbd.overflow_max_grants)) { - goto out; - } - if (work_busy(&ring->persistent_purge_work)) { pr_alert_ratelimited("Scheduled work from previous purge is still busy, cannot purge list\n"); goto out; } - num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN; - num_clean = ring->persistent_gnt_c - xen_blkif_max_pgrants + num_clean; - num_clean = min(ring->persistent_gnt_c, num_clean); - if ((num_clean == 0) || - (num_clean > (ring->persistent_gnt_c - atomic_read(&ring->persistent_gnt_in_use)))) - goto out; + if (ring->persistent_gnt_c < xen_blkif_max_pgrants || + (ring->persistent_gnt_c == xen_blkif_max_pgrants && + !ring->blkif->vbd.overflow_max_grants)) { + num_clean = 0; + } else { + num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN; + num_clean = ring->persistent_gnt_c - xen_blkif_max_pgrants + + num_clean; + num_clean = min(ring->persistent_gnt_c, num_clean); + pr_debug("Going to purge at least %u persistent grants\n", + num_clean); + } /* * At this point, we can assure that there will be no calls @@ -401,9 +420,7 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring) * number of grants. */ - total = num_clean; - - pr_debug("Going to purge %u persistent grants\n", num_clean); + total = 0; BUG_ON(!list_empty(&ring->persistent_purge_list)); root = &ring->persistent_gnts; @@ -412,46 +429,37 @@ purge_list: BUG_ON(persistent_gnt->handle == BLKBACK_INVALID_HANDLE); - if (clean_used) { - clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags); - continue; - } - if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags)) continue; - if (!scan_used && - (test_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags))) + if (!scan_used && !persistent_gnt_timeout(persistent_gnt)) + continue; + if (scan_used && total >= num_clean) continue; rb_erase(&persistent_gnt->node, root); list_add(&persistent_gnt->remove_node, &ring->persistent_purge_list); - if (--num_clean == 0) - goto finished; + total++; } /* - * If we get here it means we also need to start cleaning + * Check whether we also need to start cleaning * grants that were used since last purge in order to cope * with the requested num */ - if (!scan_used && !clean_used) { - pr_debug("Still missing %u purged frames\n", num_clean); + if (!scan_used && total < num_clean) { + pr_debug("Still missing %u purged frames\n", num_clean - total); scan_used = true; goto purge_list; } -finished: - if (!clean_used) { - pr_debug("Finished scanning for grants to clean, removing used flag\n"); - clean_used = true; - goto purge_list; - } - ring->persistent_gnt_c -= (total - num_clean); - ring->blkif->vbd.overflow_max_grants = 0; + if (total) { + ring->persistent_gnt_c -= total; + ring->blkif->vbd.overflow_max_grants = 0; - /* We can defer this work */ - schedule_work(&ring->persistent_purge_work); - pr_debug("Purged %u/%u\n", (total - num_clean), total); + /* We can defer this work */ + schedule_work(&ring->persistent_purge_work); + pr_debug("Purged %u/%u\n", num_clean, total); + } out: return; diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index ecb35fe8ca8d..7bff72db3b7e 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -234,14 +234,9 @@ struct xen_vbd { struct backend_info; /* Number of available flags */ -#define PERSISTENT_GNT_FLAGS_SIZE 2 +#define PERSISTENT_GNT_FLAGS_SIZE 1 /* This persistent grant is currently in use */ #define PERSISTENT_GNT_ACTIVE 0 -/* - * This persistent grant has been used, this flag is set when we remove the - * PERSISTENT_GNT_ACTIVE, to know that this grant has been used recently. - */ -#define PERSISTENT_GNT_WAS_ACTIVE 1 /* Number of requests that we can fit in a ring */ #define XEN_BLKIF_REQS_PER_PAGE 32 @@ -250,6 +245,7 @@ struct persistent_gnt { struct page *page; grant_ref_t gnt; grant_handle_t handle; + unsigned long last_used; DECLARE_BITMAP(flags, PERSISTENT_GNT_FLAGS_SIZE); struct rb_node node; struct list_head remove_node; -- cgit v1.2.3 From a46b53672b2c2e3770b38a4abf90d16364d2584b Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Mon, 13 Aug 2018 16:01:11 +0200 Subject: xen/blkfront: cleanup stale persistent grants MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Roger Pau Monné Signed-off-by: Konrad Rzeszutek Wilk --- drivers/block/xen-blkfront.c | 94 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 90 insertions(+), 4 deletions(-) (limited to 'drivers/block') diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 8986adab9bf5..a2a395f85a41 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -46,6 +46,7 @@ #include #include #include +#include #include #include @@ -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); -- cgit v1.2.3 From 4bcddbae019df2614ea36976ba3d36313f93c6d3 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Mon, 13 Aug 2018 16:01:12 +0200 Subject: xen/blkfront: reorder tests in xlblk_init() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In case we don't want pv block devices we should not test parameters for sanity and eventually print out error messages. So test precluding conditions before checking parameters. Signed-off-by: Juergen Gross Reviewed-by: Roger Pau Monné Signed-off-by: Konrad Rzeszutek Wilk --- drivers/block/xen-blkfront.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) (limited to 'drivers/block') diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index a2a395f85a41..a71d817e900d 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -2708,6 +2708,15 @@ static int __init xlblk_init(void) if (!xen_domain()) return -ENODEV; + if (!xen_has_pv_disk_devices()) + return -ENODEV; + + if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) { + pr_warn("xen_blk: can't get major %d with name %s\n", + XENVBD_MAJOR, DEV_NAME); + return -ENODEV; + } + if (xen_blkif_max_segments < BLKIF_MAX_SEGMENTS_PER_REQUEST) xen_blkif_max_segments = BLKIF_MAX_SEGMENTS_PER_REQUEST; @@ -2723,15 +2732,6 @@ static int __init xlblk_init(void) xen_blkif_max_queues = nr_cpus; } - if (!xen_has_pv_disk_devices()) - return -ENODEV; - - if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) { - printk(KERN_WARNING "xen_blk: can't get major %d with name %s\n", - XENVBD_MAJOR, DEV_NAME); - return -ENODEV; - } - INIT_DELAYED_WORK(&blkfront_work, blkfront_delay_work); ret = xenbus_register_frontend(&blkfront_driver); -- cgit v1.2.3 From d77ff24e7fa2258877fa0b87efa06b9a58a37aab Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Mon, 13 Aug 2018 16:01:13 +0200 Subject: xen/blkback: move persistent grants flags to bool MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The struct persistent_gnt flags member is meant to be a bitfield of different flags. There is only PERSISTENT_GNT_ACTIVE flag left, so convert it to a bool named "active". Signed-off-by: Juergen Gross Reviewed-by: Roger Pau Monné Signed-off-by: Konrad Rzeszutek Wilk --- drivers/block/xen-blkback/blkback.c | 13 ++++++------- drivers/block/xen-blkback/common.h | 7 +------ 2 files changed, 7 insertions(+), 13 deletions(-) (limited to 'drivers/block') diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index 9eae7b243f68..fd1e19f1a49f 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -255,8 +255,7 @@ static int add_persistent_gnt(struct xen_blkif_ring *ring, } } - bitmap_zero(persistent_gnt->flags, PERSISTENT_GNT_FLAGS_SIZE); - set_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags); + persistent_gnt->active = true; /* Add new node and rebalance tree. */ rb_link_node(&(persistent_gnt->node), parent, new); rb_insert_color(&(persistent_gnt->node), &ring->persistent_gnts); @@ -280,11 +279,11 @@ static struct persistent_gnt *get_persistent_gnt(struct xen_blkif_ring *ring, else if (gref > data->gnt) node = node->rb_right; else { - if(test_bit(PERSISTENT_GNT_ACTIVE, data->flags)) { + if (data->active) { pr_alert_ratelimited("requesting a grant already in use\n"); return NULL; } - set_bit(PERSISTENT_GNT_ACTIVE, data->flags); + data->active = true; atomic_inc(&ring->persistent_gnt_in_use); return data; } @@ -295,10 +294,10 @@ static struct persistent_gnt *get_persistent_gnt(struct xen_blkif_ring *ring, static void put_persistent_gnt(struct xen_blkif_ring *ring, struct persistent_gnt *persistent_gnt) { - if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags)) + if (!persistent_gnt->active) pr_alert_ratelimited("freeing a grant already unused\n"); persistent_gnt->last_used = jiffies; - clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags); + persistent_gnt->active = false; atomic_dec(&ring->persistent_gnt_in_use); } @@ -429,7 +428,7 @@ purge_list: BUG_ON(persistent_gnt->handle == BLKBACK_INVALID_HANDLE); - if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags)) + if (persistent_gnt->active) continue; if (!scan_used && !persistent_gnt_timeout(persistent_gnt)) continue; diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index 7bff72db3b7e..2339b8d39c5e 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -233,11 +233,6 @@ struct xen_vbd { struct backend_info; -/* Number of available flags */ -#define PERSISTENT_GNT_FLAGS_SIZE 1 -/* This persistent grant is currently in use */ -#define PERSISTENT_GNT_ACTIVE 0 - /* Number of requests that we can fit in a ring */ #define XEN_BLKIF_REQS_PER_PAGE 32 @@ -246,7 +241,7 @@ struct persistent_gnt { grant_ref_t gnt; grant_handle_t handle; unsigned long last_used; - DECLARE_BITMAP(flags, PERSISTENT_GNT_FLAGS_SIZE); + bool active; struct rb_node node; struct list_head remove_node; }; -- cgit v1.2.3 From 6f2f39ad1a54978394851c05e327419ebeb7227e Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Mon, 13 Aug 2018 16:01:14 +0200 Subject: xen/blkback: remove unused pers_gnts_lock from struct xen_blkif_ring MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit pers_gnts_lock isn't being used anywhere. Remove it. Signed-off-by: Juergen Gross Reviewed-by: Roger Pau Monné Signed-off-by: Konrad Rzeszutek Wilk --- drivers/block/xen-blkback/common.h | 1 - 1 file changed, 1 deletion(-) (limited to 'drivers/block') diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index 2339b8d39c5e..1d3002d773f7 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -269,7 +269,6 @@ struct xen_blkif_ring { wait_queue_head_t pending_free_wq; /* Tree to store persistent grants. */ - spinlock_t pers_gnts_lock; struct rb_root persistent_gnts; unsigned int persistent_gnt_c; atomic_t persistent_gnt_in_use; -- cgit v1.2.3