linux-ext4 - [Bug 12672] lockdep warning when using ext4 on x86

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Date:	Mon,  9 Feb 2009 02:09:10 -0800 (PST)
From:	bugme-daemon@...zilla.kernel.org
To:	linux-ext4@...r.kernel.org
Subject: [Bug 12672] lockdep warning when using ext4 on x86_64

http://bugzilla.kernel.org/show_bug.cgi?id=12672





------- Comment #2 from aneesh.kumar@...ux.vnet.ibm.com  2009-02-09 02:09 -------

Updated patch

From: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH] ext4: Fix lockdep warning

We should not call ext4_mb_add_n_trim while holding alloc_semp.

=============================================
[ INFO: possible recursive locking detected ]
2.6.29-rc4-git1-dirty #124
---------------------------------------------
ffsb/3116 is trying to acquire lock:
 (&meta_group_info[i]->alloc_sem){----}, at: [<ffffffff8035a6e8>]
 ext4_mb_load_buddy+0xd2/0x343

but task is already holding lock:
 (&meta_group_info[i]->alloc_sem){----}, at: [<ffffffff8035a6e8>]
 ext4_mb_load_buddy+0xd2/0x343

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>

 fs/ext4/mballoc.c |   29 ++++++++++++++++-------------
 1 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index deba54f..2b5ffe7 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4476,23 +4476,26 @@ static int ext4_mb_release_context(struct
ext4_allocation_context *ac)
                        pa->pa_free -= ac->ac_b_ex.fe_len;
                        pa->pa_len -= ac->ac_b_ex.fe_len;
                        spin_unlock(&pa->pa_lock);
-                       /*
-                        * We want to add the pa to the right bucket.
-                        * Remove it from the list and while adding
-                        * make sure the list to which we are adding
-                        * doesn't grow big.
-                        */
-                       if (likely(pa->pa_free)) {
-                               spin_lock(pa->pa_obj_lock);
-                               list_del_rcu(&pa->pa_inode_list);
-                               spin_unlock(pa->pa_obj_lock);
-                               ext4_mb_add_n_trim(ac);
-                       }
                }
-               ext4_mb_put_pa(ac, ac->ac_sb, pa);
        }
        if (ac->alloc_semp)
                up_read(ac->alloc_semp);
+       if (pa) {
+               /**
+                * We want to add the pa to the right bucket.
+                * Remove it from the list and while adding
+                * make sure the list to which we are adding
+                * doesn't grow big. We need to release
+                * alloc_semp before calling ext4_mb_add_n_trim()
+                */
+               if (pa->pa_linear && likely(pa->pa_free)) {
+                       spin_lock(pa->pa_obj_lock);
+                       list_del_rcu(&pa->pa_inode_list);
+                       spin_unlock(pa->pa_obj_lock);
+                       ext4_mb_add_n_trim(ac);
+               }
+               ext4_mb_put_pa(ac, ac->ac_sb, pa);
+       }
        if (ac->ac_bitmap_page)
                page_cache_release(ac->ac_bitmap_page);
        if (ac->ac_buddy_page)


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