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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 <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2011-11-02 16:29:45 +01:00 committed by Philipp Reisner
parent e89868a092
commit 763eb63625
1 changed files with 11 additions and 7 deletions
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18
drivers/block/drbd/drbd_actlog.c
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@ -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();
ext->rs_failed, count,
drbd_conn_str(mdev->state.conn));
lc_put(mdev->resync, &ext->lce);
drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
return;
/* 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,