xen/grant-table: log the lack of grants

Orabug: 26324349

log a message when we enter this situation:
1) we already allocated the max number of available grants from hypervisor
and
2) we still need more (but the request fails because of 1)).

Sometimes the lack of grants causes IO hangs in xen_blkfront devices.
Adding this log would help debuging.

Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Junxiao Bi <junxiao.bi@oracle.com>

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index effbaf91791f4d5ab7a8e0b9d195901f539a7c91..f6087f754e76f8f0e092fba6ddf00f6f460289bf 100644 (file)
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -43,6 +43,7 @@
 #include <linux/delay.h>
 #include <linux/hardirq.h>
 #include <linux/workqueue.h>
+#include <linux/ratelimit.h>
 
 #include <xen/xen.h>
 #include <xen/interface/xen.h>
@@ -1073,8 +1074,14 @@ static int gnttab_expand(unsigned int req_entries)
        cur = nr_grant_frames;
        extra = ((req_entries + (grefs_per_grant_frame-1)) /
                 grefs_per_grant_frame);
-       if (cur + extra > gnttab_max_grant_frames())
+       if (cur + extra > gnttab_max_grant_frames()) {
+               pr_warn_ratelimited("xen/grant-table: max_grant_frames reached"
+                                   " cur=%u extra=%u limit=%u"
+                                   " gnttab_free_count=%u req_entries=%u\n",
+                                   cur, extra, gnttab_max_grant_frames(),
+                                   gnttab_free_count, req_entries);
                return -ENOSPC;
+       }
 
        rc = gnttab_map(cur, cur + extra - 1);
        if (rc == 0)