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authorJonathan Brassow <jbrassow@redhat.com>2009-09-04 20:40:32 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2009-09-15 10:45:32 -0700
commit8c57b59008353a5e218c12bccb8bd1c2cf7ea5d9 (patch)
treea0a27f445601050cbe7d4d05d5d21914007d096a
parent8f78d18b849ef860dccfa636b209a48e5a34a410 (diff)
downloadlwn-8c57b59008353a5e218c12bccb8bd1c2cf7ea5d9.tar.gz
lwn-8c57b59008353a5e218c12bccb8bd1c2cf7ea5d9.zip
dm raid1: do not allow log_failure variable to unset after being set
commit d2b698644c97cb033261536a4f2010924a00eac9 upstream. This patch fixes a bug which was triggering a case where the primary leg could not be changed on failure even when the mirror was in-sync. The case involves the failure of the primary device along with the transient failure of the log device. The problem is that bios can be put on the 'failures' list (due to log failure) before 'fail_mirror' is called due to the primary device failure. Normally, this is fine, but if the log device failure is transient, a subsequent iteration of the work thread, 'do_mirror', will reset 'log_failure'. The 'do_failures' function then resets the 'in_sync' variable when processing bios on the failures list. The 'in_sync' variable is what is used to determine if the primary device can be switched in the event of a failure. Since this has been reset, the primary device is incorrectly assumed to be not switchable. The case has been seen in the cluster mirror context, where one machine realizes the log device is dead before the other machines. As the responsibilities of the server migrate from one node to another (because the mirror is being reconfigured due to the failure), the new server may think for a moment that the log device is fine - thus resetting the 'log_failure' variable. In any case, it is inappropiate for us to reset the 'log_failure' variable. The above bug simply illustrates that it can actually hurt us. Signed-off-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/md/dm-raid1.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index d8d31b85607d..a2cf5cf3d856 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -648,7 +648,13 @@ static void do_writes(struct mirror_set *ms, struct bio_list *writes)
*/
dm_rh_inc_pending(ms->rh, &sync);
dm_rh_inc_pending(ms->rh, &nosync);
- ms->log_failure = dm_rh_flush(ms->rh) ? 1 : 0;
+
+ /*
+ * If the flush fails on a previous call and succeeds here,
+ * we must not reset the log_failure variable. We need
+ * userspace interaction to do that.
+ */
+ ms->log_failure = dm_rh_flush(ms->rh) ? 1 : ms->log_failure;
/*
* Dispatch io.