From: NeilBrown <neilb@cse.unsw.edu.au>
If one md array is waiting for another to finish resyncing, then it holds a
reference to the array, so the array cannot be stopped. With this patch, we
drop the reference before waiting.
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/drivers/md/md.c | 53 ++++++++++++++++++++++++++++++++----------------
1 files changed, 36 insertions(+), 17 deletions(-)
diff -puN drivers/md/md.c~md-dont-hold-lock-on-md-devices-while-waiting-for-them-to-finish-resync drivers/md/md.c
--- 25/drivers/md/md.c~md-dont-hold-lock-on-md-devices-while-waiting-for-them-to-finish-resync Wed Oct 20 16:01:52 2004
+++ 25-akpm/drivers/md/md.c Wed Oct 20 16:01:52 2004
@@ -3378,33 +3378,54 @@ static void md_do_sync(mddev_t *mddev)
* 1 == like 2, but have yielded to allow conflicting resync to
* commense
* other == active in resync - this many blocks
+ *
+ * Before starting a resync we must have set curr_resync to
+ * 2, and then checked that every "conflicting" array has curr_resync
+ * less than ours. When we find one that is the same or higher
+ * we wait on resync_wait. To avoid deadlock, we reduce curr_resync
+ * to 1 if we choose to yield (based arbitrarily on address of mddev structure).
+ * This will mean we have to start checking from the beginning again.
+ *
*/
+
do {
mddev->curr_resync = 2;
+ try_again:
+ if (signal_pending(current)) {
+ flush_signals(current);
+ goto skip;
+ }
ITERATE_MDDEV(mddev2,tmp) {
+ printk(".");
if (mddev2 == mddev)
continue;
if (mddev2->curr_resync &&
match_mddev_units(mddev,mddev2)) {
- printk(KERN_INFO "md: delaying resync of %s"
- " until %s has finished resync (they"
- " share one or more physical units)\n",
- mdname(mddev), mdname(mddev2));
- if (mddev < mddev2) {/* arbitrarily yield */
+ DEFINE_WAIT(wq);
+ if (mddev < mddev2 && mddev->curr_resync == 2) {
+ /* arbitrarily yield */
mddev->curr_resync = 1;
wake_up(&resync_wait);
}
- if (wait_event_interruptible(resync_wait,
- mddev2->curr_resync < mddev->curr_resync)) {
- flush_signals(current);
+ if (mddev > mddev2 && mddev->curr_resync == 1)
+ /* no need to wait here, we can wait the next
+ * time 'round when curr_resync == 2
+ */
+ continue;
+ prepare_to_wait(&resync_wait, &wq, TASK_INTERRUPTIBLE);
+ if (!signal_pending(current)
+ && mddev2->curr_resync >= mddev->curr_resync) {
+ printk(KERN_INFO "md: delaying resync of %s"
+ " until %s has finished resync (they"
+ " share one or more physical units)\n",
+ mdname(mddev), mdname(mddev2));
mddev_put(mddev2);
- goto skip;
+ schedule();
+ finish_wait(&resync_wait, &wq);
+ goto try_again;
}
- }
- if (mddev->curr_resync == 1) {
- mddev_put(mddev2);
- break;
+ finish_wait(&resync_wait, &wq);
}
}
} while (mddev->curr_resync < 2);
@@ -3552,6 +3573,7 @@ static void md_do_sync(mddev_t *mddev)
md_enter_safemode(mddev);
skip:
mddev->curr_resync = 0;
+ wake_up(&resync_wait);
set_bit(MD_RECOVERY_DONE, &mddev->recovery);
md_wakeup_thread(mddev->thread);
}
@@ -3619,15 +3641,12 @@ void md_check_recovery(mddev_t *mddev)
mddev->recovery = 0;
/* flag recovery needed just to double check */
set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
- wake_up(&resync_wait);
md_new_event();
goto unlock;
}
- if (mddev->recovery) {
+ if (mddev->recovery)
/* probably just the RECOVERY_NEEDED flag */
mddev->recovery = 0;
- wake_up(&resync_wait);
- }
/* no recovery is running.
* remove any failed drives, then
_