[Devel] [PATCH hci-8.1 v2 4/4] dm-ploop: fix a failed cluster copy on grow leaving the BAT page busy

[Denis V. Lunev]

From: Denis V. Lunev <den at openvz.org>

ploop_prepare_reloc_index_wb() marks the BAT page of a relocated
cluster MD_UPDATING and MD_DIRTY and allocates the cluster to copy it
to. When ploop_write_cluster_sync() then fails, an I/O error or ENOSPC
on the host file system, ploop_grow_relocate_cluster() only frees the
piwb. The resize fails and submission resumes with both bits set:

- every allocating write, discard or COW on a cluster of that page is
  parked in md->wait_llist, which only a writeback completion of the
  page drains, and none comes. These requests never complete, a dm
  suspend of the device hangs and later ploop cmds time out in the
  inflight ref switch;

- the allocated cluster stays taken in holes_bitmap until the image is
  reopened.

Clear the bits as the error path of ploop_prepare_reloc_index_wb()
does and give the cluster back. Submission is stopped for the whole
resize, so no pio waits on the page and none has to be resubmitted.

Fixes: 018063db0eeb ("dm-ploop: fix resize and grow to use the new way of updating md pages")
Reported-by: Konstantin Khorenko <khorenko at virtuozzo.com>
https://virtuozzo.atlassian.net/browse/VSTOR-152981
Feature: dm-ploop: ploop target driver
Reviewed-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
Reviewed-by: Konstantin Khorenko <khorenko at virtuozzo.com>
Signed-off-by: Denis V. Lunev <den at openvz.org>
---
 drivers/md/dm-ploop-cmd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/md/dm-ploop-cmd.c b/drivers/md/dm-ploop-cmd.c
index 29f9a7ee7540..1cb186a2e0cd 100644
--- a/drivers/md/dm-ploop-cmd.c
+++ b/drivers/md/dm-ploop-cmd.c
@@ -351,6 +351,12 @@ static int ploop_grow_relocate_cluster(struct ploop *ploop,
 		PL_ERR("reloc: failed write: %d", ret);
 		/* piwb can not change here we are the only user of md page */
 		ploop_break_bat_update(ploop, md, piwb);
+		spin_lock_irq(&ploop->bat_lock);
+		if (add_for_wb)
+			clear_bit(MD_DIRTY, &md->status);
+		clear_bit(MD_UPDATING, &md->status);
+		ploop_hole_set_bit(new_dst, ploop);
+		spin_unlock_irq(&ploop->bat_lock);
 		goto out;
 	}
 
-- 
2.53.0