md: don't print the same repeated messages about delayed sync operation

This fixes a long-standing bug that caused a flood of messages like:
"md: delaying data-check of md1 until md2 has finished (they share one
or more physical units)"

It can be reproduced like this:
1. Create at least 3 raid1 arrays on a pair of disks, each on different
   partitions.
2. Request a sync operation like 'check' or 'repair' on 2 arrays by
   writing to their md/sync_action attribute files. One operation should
   start and one should be delayed and a message like the above will be
   printed.
3. Issue a write to the third array. Each write will cause 2 copies of
   the message to be printed.

This happens when wake_up(&resync_wait) is called, usually by
md_check_recovery(). Then the delayed sync thread again prints the
message and is put to sleep. This patch adds a check in md_do_sync() to
prevent printing this message more than once for the same pair of
devices.

Reported-by: Sven Koehler <sven.koehler@gmail.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=151801
Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 19d8e23bda5ce37e11605d6639aad62457e946fb..cc25cbcf10b25c609248eb6553d2ef5464fa8e7a 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7865,6 +7865,7 @@ void md_do_sync(struct md_thread *thread)
         */
 
        do {
+               int mddev2_minor = -1;
                mddev->curr_resync = 2;
 
        try_again:
@@ -7894,10 +7895,14 @@ void md_do_sync(struct md_thread *thread)
                                prepare_to_wait(&resync_wait, &wq, TASK_INTERRUPTIBLE);
                                if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
                                    mddev2->curr_resync >= mddev->curr_resync) {
-                                       printk(KERN_INFO "md: delaying %s of %s"
-                                              " until %s has finished (they"
-                                              " share one or more physical units)\n",
-                                              desc, mdname(mddev), mdname(mddev2));
+                                       if (mddev2_minor != mddev2->md_minor) {
+                                               mddev2_minor = mddev2->md_minor;
+                                               printk(KERN_INFO "md: delaying %s of %s"
+                                                      " until %s has finished (they"
+                                                      " share one or more physical units)\n",
+                                                      desc, mdname(mddev),
+                                                      mdname(mddev2));
+                                       }
                                        mddev_put(mddev2);
                                        if (signal_pending(current))
                                                flush_signals(current);