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? Thanks, Song -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
