On Mon, Feb 15, 2021 at 3:08 AM Paul Menzel <[email protected]> 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/[email protected]/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 <[email protected]>
> > Signed-off-by: Guoqing Jiang <[email protected]>
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
[email protected]
https://listman.redhat.com/mailman/listinfo/dm-devel
