From: Lars Ellenberg Date: Wed, 2 Nov 2011 15:29:45 +0000 (+0100) Subject: drbd: fix potential spinlock deadlock X-Git-Tag: firefly_0821_release~3680^2~2719^2^2~30 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=763eb63625a625e4d160cbb4cce2bcdb40141b97;p=firefly-linux-kernel-4.4.55.git drbd: fix potential spinlock deadlock drbd_try_clear_on_disk_bm() has a sanity check for the number of blocks left to be resynced (rs_left) in the current resync extent. If it detects a mismatch, it complains, and forces a disconnect using drbd_force_state(mdev, NS(conn, C_DISCONNECTING)); Unfortunately, this may be called while holding the req_lock, and drbd_force_state() want's to aquire that lock itself. Deadlock. Don't force a disconnect, but fix up rs_left by recounting and reassigning the number of dirty blocks in that extent. Signed-off-by: Philipp Reisner Signed-off-by: Lars Ellenberg --- diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c index 3d7c2153daca..601ad9ef0437 100644 --- a/drivers/block/drbd/drbd_actlog.c +++ b/drivers/block/drbd/drbd_actlog.c @@ -711,16 +711,20 @@ static void drbd_try_clear_on_disk_bm(struct drbd_conf *mdev, sector_t sector, else ext->rs_failed += count; if (ext->rs_left < ext->rs_failed) { - dev_err(DEV, "BAD! sector=%llus enr=%u rs_left=%d " - "rs_failed=%d count=%d\n", + dev_warn(DEV, "BAD! sector=%llus enr=%u rs_left=%d " + "rs_failed=%d count=%d cstate=%s\n", (unsigned long long)sector, ext->lce.lc_number, ext->rs_left, - ext->rs_failed, count); - dump_stack(); - - lc_put(mdev->resync, &ext->lce); - drbd_force_state(mdev, NS(conn, C_DISCONNECTING)); - return; + ext->rs_failed, count, + drbd_conn_str(mdev->state.conn)); + + /* We don't expect to be able to clear more bits + * than have been set when we originally counted + * the set bits to cache that value in ext->rs_left. + * Whatever the reason (disconnect during resync, + * delayed local completion of an application write), + * try to fix it up by recounting here. */ + ext->rs_left = drbd_bm_e_weight(mdev, enr); } } else { /* Normally this element should be in the cache,