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xen/grant-table: log the lack of grants 

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>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Wengang Wang 2017-07-18 09:40:35 +02:00 committed by Juergen Gross
parent 0e4d394fe5
commit 29d11cfd86
1 changed files with 8 additions and 1 deletions
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9
drivers/xen/grant-table.c
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@ -42,6 +42,7 @@
#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>
@ -1072,8 +1073,14 @@ 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)