On 2/24/21 10:09, Song Liu wrote:
On Mon, Feb 15, 2021 at 3:08 AM Paul Menzel <pmenzel@xxxxxxxxxxxxx> wrote:
[+cc Donald]
Am 13.02.21 um 01:49 schrieb Guoqing Jiang:
Unregister sync_thread doesn't need to hold reconfig_mutex since it
doesn't reconfigure array.
And it could cause deadlock problem for raid5 as follows:
1. process A tried to reap sync thread with reconfig_mutex held after echo
idle to sync_action.
2. raid5 sync thread was blocked if there were too many active stripes.
3. SB_CHANGE_PENDING was set (because of write IO comes from upper layer)
which causes the number of active stripes can't be decreased.
4. SB_CHANGE_PENDING can't be cleared since md_check_recovery was not able
to hold reconfig_mutex.
More details in the link:
https://lore.kernel.org/linux-raid/5ed54ffc-ce82-bf66-4eff-390cb23bc1ac@xxxxxxxxxxxxx/T/#t
And add one parameter to md_reap_sync_thread since it could be called by
dm-raid which doesn't hold reconfig_mutex.
Reported-and-tested-by: Donald Buczek <buczek@xxxxxxxxxxxxx>
Signed-off-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>
I don't really like this fix. But I haven't got a better (and not too
complicated)
alternative.
---
V2:
1. add one parameter to md_reap_sync_thread per Jack's suggestion.
drivers/md/dm-raid.c | 2 +-
drivers/md/md.c | 14 +++++++++-----
drivers/md/md.h | 2 +-
3 files changed, 11 insertions(+), 7 deletions(-)
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index cab12b2..0c4cbba 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3668,7 +3668,7 @@ static int raid_message(struct dm_target *ti, unsigned int argc, char **argv,
if (!strcasecmp(argv[0], "idle") || !strcasecmp(argv[0], "frozen")) {
if (mddev->sync_thread) {
set_bit(MD_RECOVERY_INTR, &mddev->recovery);
- md_reap_sync_thread(mddev);
+ md_reap_sync_thread(mddev, false);
I think we can add mddev_lock() and mddev_unlock() here and then we don't
need the extra parameter?
I thought it too, but I would prefer get the input from DM people first.
@ Mike or Alasdair
Thanks,
Guoqing
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