[PATCH v2 0/3] ocfs2: cluster: o2hb_region_pin() fixes

[Joseph Qi <joseph.qi@linux.alibaba.com>]

This series fixes three related issues in o2hb_region_pin(), all are
from the original implementation in commit:
58a3158a5d17 ("ocfs2/cluster: Pin/unpin o2hb regions"):

1) It is called with o2hb_live_lock (a spinlock) held, but the
   underlying configfs_depend_item() sleeps (takes inode rwsem and
   pins the filesystem).  This triggers BUG under
   CONFIG_DEBUG_ATOMIC_SLEEP.

2) When called from the configfs drop_item callback, it creates a
   lock order inversion: parent inode_lock -> configfs root
   inode_lock, which can deadlock against subsystem unregistration
   paths taking root -> parent.

3) If pinning fails partway through o2hb_region_inc_user(), the
   o2hb_dependent_users counter is leaked and partially-pinned
   regions are never released, leaving heartbeat regions
   unprotected on subsequent mounts.

Patch 1 reworks o2hb_region_pin() to drop o2hb_live_lock across
each sleeping configfs_depend_item() call, using a config_item
reference to keep the region alive while unlocked.

Patch 2 adds a from_callback parameter to select
configfs_depend_item_unlocked() when called from configfs context,
avoiding the inode_lock nesting.

Patch 3 fixes the error path in o2hb_region_inc_user() to unpin
and decrement the counter on failure.

Joseph Qi (3):
  ocfs2: cluster: don't sleep while holding o2hb_live_lock in
    o2hb_region_pin()
  ocfs2: cluster: avoid lock order inversion in o2hb_region_pin() from
    drop_item
  ocfs2: cluster: fix o2hb_dependent_users leak on pin failure

 fs/ocfs2/cluster/heartbeat.c   | 146 ++++++++++++++++++++++++++-------
 fs/ocfs2/cluster/nodemanager.c |   6 ++
 fs/ocfs2/cluster/nodemanager.h |   1 +
 3 files changed, 122 insertions(+), 31 deletions(-)

-- 
2.39.3