[PATCH 3.12 001/182] dlm: Avoid that dlm_release_lockspace() incorrectly returns -EBUSY

Jiri Slaby
2014-05-13T10:46:44Z

From: Bart Van Assche <bvanassche@acm.org>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit a97f4a66d8ee4faf0f31cc4ad3f4aa0baef23fc7 upstream.

When dlm_release_lockspace(ls, 1) is invoked on a busy system
immediately after the last dlm_unlock() AST has finished it can occur
that lkb_idr_is_local() is invoked for the unlocked LKB since removal
from ls_lkbidr only occurs after the AST has returned. If that happens
dlm_release_lockspace(ls, 1) will return -EBUSY instead of releasing
the lockspace. Fix this race condition by changing lkb_idr_is_local()
such that it only returns true for LKB's that have not yet been
unlocked.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
fs/dlm/lockspace.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/dlm/lockspace.c b/fs/dlm/lockspace.c
index 88556dc0458e..d5abafd56a6d 100644
--- a/fs/dlm/lockspace.c
+++ b/fs/dlm/lockspace.c
@@ -706,9 +706,7 @@ static int lkb_idr_is_local(int id, void *p, void *data)
{
struct dlm_lkb *lkb = p;

- if (!lkb->lkb_nodeid)
- return 1;
- return 0;
+ return lkb->lkb_nodeid == 0 && lkb->lkb_grmode != DLM_LOCK_IV;
}

static int lkb_idr_is_any(int id, void *p, void *data)
--
1.9.3