Commit c622ca54 authored Aug 16, 2016 by Artur Paszkiewicz Committed by Shaohua Li Aug 17, 2016

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>

parent 207efcd2

drivers/md/md.c

+9 −4

Original line number	Diff line number	Diff line
		@@ -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) {
		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));
		desc, mdname(mddev),
		mdname(mddev2));
		}
		mddev_put(mddev2);
		if (signal_pending(current))
		flush_signals(current);

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