Prevent blkfront from hoarding all grants by adding a minimum number
of grants that must be free at all times. We still need a way to free
unused grants in blkfront, but this patch will mitigate the problem
in the meantime.
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
---
drivers/block/xen-blkfront.c | 10 ++++++++--
1 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 187a437..3d445c0 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -101,6 +101,12 @@ MODULE_PARM_DESC(max, "Maximum amount of segments in
indirect requests (default
#define BLK_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE)
/*
+ * Make sure there are at least MIN_FREE_GRANTS at all times, preventing
+ * blkfront from hoarding all grants
+ */
+#define MIN_FREE_GRANTS 512
+
+/*
* We have one of these per vbd, whether ide, scsi or 'other'. They
* hang in private_data off the gendisk structure. We may end up
* putting all kinds of interesting stuff here :-)
@@ -412,13 +418,13 @@ static int blkif_queue_request(struct request *req)
if (info->persistent_gnts_c < max_grefs) {
new_persistent_gnts = 1;
if (gnttab_alloc_grant_references(
- max_grefs - info->persistent_gnts_c,
+ max_grefs - info->persistent_gnts_c + MIN_FREE_GRANTS,
&gref_head) < 0) {
gnttab_request_free_callback(
&info->callback,
blkif_restart_queue_callback,
info,
- max_grefs);
+ max_grefs + MIN_FREE_GRANTS);
return 1;
}
} else
--
1.7.7.5 (Apple Git-26)
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