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Subject[PATCH 29/30] configfs: dir.c fix possible recursive locking
Date
From: Joonwoo Park <joonwpark81@gmail.com>

configfs_register_subsystem() with default_groups triggers recursive locking.
it seems that mutex_lock_nested is needed.

=============================================
[ INFO: possible recursive locking detected ]
2.6.24-rc6 #141
---------------------------------------------
swapper/1 is trying to acquire lock:
(&sb->s_type->i_mutex_key#3){--..}, at: [<c40ca76f>] configfs_attach_group+0x4f/0x190
but task is already holding lock:
(&sb->s_type->i_mutex_key#3){--..}, at: [<c40ca9d5>] configfs_register_subsystem+0x55/0x130
other info that might help us debug this:
1 lock held by swapper/1:
#0: (&sb->s_type->i_mutex_key#3){--..}, at: [<c40ca9d5>] configfs_register_subsystem+0x55/0x130
stack backtrace:
Pid: 1, comm: swapper Not tainted 2.6.24-rc6 #141
[<c40053ba>] show_trace_log_lvl+0x1a/0x30
[<c4005e82>] show_trace+0x12/0x20
[<c400687e>] dump_stack+0x6e/0x80
[<c404ec72>] __lock_acquire+0xe62/0x1120
[<c404efb2>] lock_acquire+0x82/0xa0
[<c43fdad8>] mutex_lock_nested+0x98/0x2e0
[<c40ca76f>] configfs_attach_group+0x4f/0x190
[<c40caa46>] configfs_register_subsystem+0xc6/0x130
[<c45c8186>] init_netconsole+0x2b6/0x300
[<c45a75f2>] kernel_init+0x142/0x320
[<c4004fb3>] kernel_thread_helper+0x7/0x14
=======================
Signed-off-by: Joonwoo Park <joonwpark81@gmail.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
---
fs/configfs/dir.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 50ed691..a48dc7d 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -546,7 +546,7 @@ static int populate_groups(struct config_group *group)
* That said, taking our i_mutex is closer to mkdir
* emulation, and shouldn't hurt.
*/
- mutex_lock(&dentry->d_inode->i_mutex);
+ mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);

for (i = 0; group->default_groups[i]; i++) {
new_group = group->default_groups[i];
@@ -1405,7 +1405,8 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
sd = configfs_sb->s_root->d_fsdata;
link_group(to_config_group(sd->s_element), group);

- mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);
+ mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
+ I_MUTEX_PARENT);

name.name = group->cg_item.ci_name;
name.len = strlen(name.name);
--
1.5.3.6


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