Re: Once more: Recovering a damaged ext4 fs?

[Theodore Tso <tytso@mit.edu>]

This patch *might* solve your problem.  I can't be sure because I
haven't been able to reproduce the soft lockup problem when rm'ing a
file yet.  But if it's happening fairly often, it might be worth a
try; it definitely fixes a real bug in ext4 --- I'm just not sure it's
*your* bug.  :-)

						- Ted

commit 73cda61b58a060b6691791a44c01c16155617451
Author: Theodore Ts'o <tytso@mit.edu>
Date:   Fri Mar 27 19:43:21 2009 -0400

    ext4: fix locking typo in mballoc which could cause soft lockup hangs
    
    Smatch (http://repo.or.cz/w/smatch.git/) complains about the locking in
    ext4_mb_add_n_trim() from fs/ext4/mballoc.c
    
      4438          list_for_each_entry_rcu(tmp_pa, &lg->lg_prealloc_list[order],
      4439                                                  pa_inode_list) {
      4440                  spin_lock(&tmp_pa->pa_lock);
      4441                  if (tmp_pa->pa_deleted) {
      4442                          spin_unlock(&pa->pa_lock);
      4443                          continue;
      4444                  }
    
    Brown paper bag time...
    
    Reported-by: Dan Carpenter <error27@gmail.com>
    Reviewed-by: Eric Sandeen <sandeen@redhat.com>
    Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@gmail.com>
    Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
    Cc: stable@kernel.org

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 4f2f476..12d1081 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4389,7 +4389,7 @@ static void ext4_mb_add_n_trim(struct ext4_allocation_context *ac)
 						pa_inode_list) {
 		spin_lock(&tmp_pa->pa_lock);
 		if (tmp_pa->pa_deleted) {
-			spin_unlock(&pa->pa_lock);
+			spin_unlock(&tmp_pa->pa_lock);
 			continue;
 		}
 		if (!added && pa->pa_free < tmp_pa->pa_free) {