File pvscan-retry-VG-refresh-before-autoactivation-if-it-fails.patch of Package lvm2.1005
From 54da9adbeff0e227056014455ef4cb2364af3123 Mon Sep 17 00:00:00 2001
From: Liuhua Wang <lwang@suse.com>
Date: Thu, 20 Aug 2015 11:17:03 +0800
Subject: [PATCH] pvscan: retry VG refresh before autoactivation if it fails
There's a tiny race when suspending the device which is part
of the refresh because when suspend ioctl is performed, the
dm kernel driver executes (do_suspend and dm_suspend kernel fn):
step 1: a check whether the dev is already suspended and
if yes it returns success immediately as there's
nothing to do
step 2: it grabs the suspend lock
step 3: another check whether the dev is already suspended
and if found suspended, it exits with -EINVAL now
The race can occur in between step 1 and step 2. To prevent
premature autoactivation failure, we're using a simple retry
logic here before we fail completely. For a complete solution,
we need to fix the locking so there's no possibility for suspend
calls to interleave each other to cause this kind of race.
This is just a workaround. Remove it and replace it with proper
locking once we have that in!
References: bnc#938208
Git-commit: d8085edf65006a50608edb821b3d30947abaa838
---
LVM2.2.02.98/tools/pvscan.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git LVM2.2.02.98.orig/tools/pvscan.c LVM2.2.02.98/tools/pvscan.c
index 3d5ddef..28850d5 100644
--- LVM2.2.02.98.orig/tools/pvscan.c
+++ LVM2.2.02.98/tools/pvscan.c
@@ -91,13 +91,49 @@ static void _pvscan_display_single(struct cmd_context *cmd,
display_size(cmd, (uint64_t) (pv_pe_count(pv) - pv_pe_alloc_count(pv)) * pv_pe_size(pv)));
}
+#define REFRESH_BEFORE_AUTOACTIVATION_RETRIES 5
+#define REFRESH_BEFORE_AUTOACTIVATION_RETRY_USLEEP_DELAY 100000
+
static int _auto_activation_handler(struct volume_group *vg, int partial,
activation_change_t activate)
{
+ unsigned int refresh_retries = REFRESH_BEFORE_AUTOACTIVATION_RETRIES;
+ int refresh_done = 0;
+
/* TODO: add support for partial and clustered VGs */
if (partial || vg_is_clustered(vg))
return 1;
+ /* FIXME: There's a tiny race when suspending the device which is part
+ * of the refresh because when suspend ioctl is performed, the dm
+ * kernel driver executes (do_suspend and dm_suspend kernel fn):
+ *
+ * step 1: a check whether the dev is already suspended and
+ * if yes it returns success immediately as there's
+ * nothing to do
+ * step 2: it grabs the suspend lock
+ * step 3: another check whether the dev is already suspended
+ * and if found suspended, it exits with -EINVAL now
+ *
+ * The race can occur in between step 1 and step 2. To prevent premature
+ * autoactivation failure, we're using a simple retry logic here before
+ * we fail completely. For a complete solution, we need to fix the
+ * locking so there's no possibility for suspend calls to interleave
+ * each other to cause this kind of race.
+ *
+ * Remove this workaround with "refresh_retries" once we have proper locking in!
+ */
+ while (refresh_retries--) {
+ if (vg_refresh_visible(vg->cmd, vg)) {
+ refresh_done = 1;
+ break;
+ }
+ usleep(REFRESH_BEFORE_AUTOACTIVATION_RETRY_USLEEP_DELAY);
+ }
+
+ if (!refresh_done)
+ log_warn("%s: refresh before autoactivation failed.", vg->name);
+
if (!vgchange_activate(vg->cmd, vg, activate)) {
log_error("%s: autoactivation failed.", vg->name);
return 0;
--
1.8.4.5
