When destroying a config_group having default groups, lockdep raises a warning
because multiple locks of class I_MUTEX_NORMAL are taken in
configfs_detach_prep() (the first one being in vfs_rmdir()). However this
recursive locking is another instance of I_MUTEX_PARENT -> I_MUTEX_CHILD
dependency, which was already checked correct when creating the config_group,
and which lockdep cannot handle cleanly because of the variable depth.
This patch silences lockdep when destroying default groups by simply hiding the
inode mutex locks from lockdep in configfs_detach_prep(),
configfs_detach_rollback(), and detach_groups().
=============================================
[ INFO: possible recursive locking detected ]
2.6.26-rc3 #5
---------------------------------------------
rmdir/1499 is trying to acquire lock:
(&sb->s_type->i_mutex_key#11){--..}, at: [<ffffffff802d2529>]
configfs_detach_prep+0x54/0x89
but task is already holding lock:
(&sb->s_type->i_mutex_key#11){--..}, at: [<ffffffff80296513>]
vfs_rmdir+0x49/0xac
other info that might help us debug this:
2 locks held by rmdir/1499:
#0: (&sb->s_type->i_mutex_key#3/1){--..}, at: [<ffffffff80298138>]
do_rmdir+0x82/0x108
#1: (&sb->s_type->i_mutex_key#11){--..}, at: [<ffffffff80296513>]
vfs_rmdir+0x49/0xac
stack backtrace:
Pid: 1499, comm: rmdir Not tainted 2.6.26-rc3 #5
Call Trace:
[<ffffffff8024afe9>] __lock_acquire+0x8d2/0xc78
[<ffffffff80266399>] filemap_fault+0x1cf/0x332
[<ffffffff802d2529>] configfs_detach_prep+0x54/0x89
[<ffffffff8024b762>] lock_acquire+0x51/0x6c
[<ffffffff802d2529>] configfs_detach_prep+0x54/0x89
[<ffffffff80248331>] debug_mutex_lock_common+0x16/0x23
[<ffffffff805d6244>] mutex_lock_nested+0xcd/0x23b
[<ffffffff802d2529>] configfs_detach_prep+0x54/0x89
[<ffffffff802d3656>] configfs_rmdir+0xb8/0x1c3
[<ffffffff80296535>] vfs_rmdir+0x6b/0xac
[<ffffffff8029816d>] do_rmdir+0xb7/0x108
[<ffffffff8024a2a2>] trace_hardirqs_on+0xef/0x113
[<ffffffff805d7364>] trace_hardirqs_on_thunk+0x35/0x3a
[<ffffffff8020b0cb>] system_call_after_swapgs+0x7b/0x80
Signed-off-by: Louis Rilling <[EMAIL PROTECTED]>
---
fs/configfs/dir.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
Index: b/fs/configfs/dir.c
===================================================================
--- a/fs/configfs/dir.c 2008-05-20 18:19:41.000000000 +0200
+++ b/fs/configfs/dir.c 2008-05-20 18:19:45.000000000 +0200
@@ -352,7 +352,12 @@ static int configfs_detach_prep(struct d
if (sd->s_type & CONFIGFS_NOT_PINNED)
continue;
if (sd->s_type & CONFIGFS_USET_DEFAULT) {
+ /* Hide this mutex from lockdep for the same reasons as
in
+ * populate_groups()
+ */
+ lockdep_off();
mutex_lock(&sd->s_dentry->d_inode->i_mutex);
+ lockdep_on();
/* Mark that we've taken i_mutex */
sd->s_type |= CONFIGFS_USET_DROPPING;
@@ -388,7 +393,12 @@ static void configfs_detach_rollback(str
if (sd->s_type & CONFIGFS_USET_DROPPING) {
sd->s_type &= ~CONFIGFS_USET_DROPPING;
+ /* This mutex was hidden from lockdep in
+ * configfs_detach_prep()
+ */
+ lockdep_off();
mutex_unlock(&sd->s_dentry->d_inode->i_mutex);
+ lockdep_on();
}
}
}
@@ -475,8 +485,14 @@ static void detach_groups(struct config_
* has taken our i_mutex for us. Drop it.
* From mkdir/register cleanup, there is no sem held.
*/
- if (sd->s_type & CONFIGFS_USET_DROPPING)
+ if (sd->s_type & CONFIGFS_USET_DROPPING) {
+ /* This mutex was hidden from lockdep in
+ * configfs_detach_prep()
+ */
+ lockdep_off();
mutex_unlock(&child->d_inode->i_mutex);
+ lockdep_on();
+ }
d_delete(child);
dput(child);
--
Dr Louis Rilling Kerlabs
Skype: louis.rilling Batiment Germanium
Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes
http://www.kerlabs.com/ 35700 Rennes
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