linux-kernel - [PATCH 1/2] fs/ocfs2/dlm: Eliminate update of list_for_each

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Date:	Sat, 7 Aug 2010 11:09:13 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	Mark Fasheh <mfasheh@...e.com>,
	Joel Becker <joel.becker@...cle.com>,
	ocfs2-devel@....oracle.com, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [PATCH 1/2] fs/ocfs2/dlm: Eliminate update of list_for_each_entry
 loop cursor

From: Julia Lawall <julia@...u.dk>

list_for_each_entry uses its first argument to move from one element to the
next, so modifying it can break the iteration.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@r@
iterator name list_for_each_entry;
expression x,E;
position p1,p2;
@@

list_for_each_entry@p1(x,...) { <... x =@p2 E ...> }

@@
expression x,E;
position r.p1,r.p2;
statement S;
@@

*x =@p2 E
...
list_for_each_entry@p1(x,...) S
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>

---
I don't know whether this is the right solution, but it seems plausible
considering the subsequent test on lock.  In any case, setting lock to NULL
and then going back to the top of the loop does not work.

 fs/ocfs2/dlm/dlmrecovery.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
index 9dfaac7..7084a11 100644
--- a/fs/ocfs2/dlm/dlmrecovery.c
+++ b/fs/ocfs2/dlm/dlmrecovery.c
@@ -1792,10 +1792,10 @@ static int dlm_process_recovery_data(struct dlm_ctxt *dlm,
 			for (j = DLM_GRANTED_LIST; j <= DLM_BLOCKED_LIST; j++) {
 				tmpq = dlm_list_idx_to_ptr(res, j);
 				list_for_each_entry(lock, tmpq, list) {
-					if (lock->ml.cookie != ml->cookie)
+					if (lock->ml.cookie != ml->cookie) {
 						lock = NULL;
-					else
 						break;
+					}
 				}
 				if (lock)
 					break;
--
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