diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback
index 8bb43b66eb55a1f8c0cbac1917301b2e96a55bbc..4e7babb3ba1fecc673018253d4adbb860e0cb8a4 100644
--- a/Documentation/ABI/testing/sysfs-driver-xen-blkback
+++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback
@@ -15,3 +15,13 @@ Description:
blkback. If the frontend tries to use more than
max_persistent_grants, the LRU kicks in and starts
removing 5% of max_persistent_grants every 100ms.
+
+What: /sys/module/xen_blkback/parameters/persistent_grant_unused_seconds
+Date: August 2018
+KernelVersion: 4.19
+Contact: Roger Pau Monné <roger.pau@citrix.com>
+Description:
+ How long a persistent grant is allowed to remain
+ allocated without being in use. The time is in
+ seconds, 0 means indefinitely long.
+ The default is 60 seconds.
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index b55b245e805205a07266c9d745b96e4716ed3009..9eae7b243f68b80d3407790997af4041d5150872 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 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring)
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 ecb35fe8ca8dbb54f36a85513a09064819acd67a..7bff72db3b7eb7747377f0cbc3b6cb6cf7acdcc0 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;