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Subject[PATCH 30/30] configfs: file.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 #145
---------------------------------------------
swapper/1 is trying to acquire lock:
(&sb->s_type->i_mutex_key#3){--..}, at: [<c40c9a9e>] configfs_add_file+0x2e/0x70

but task is already holding lock:
(&sb->s_type->i_mutex_key#3){--..}, at: [<c40ca985>] 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: [<c40ca985>] configfs_register_subsystem+0x55/0x130

stack backtrace:
Pid: 1, comm: swapper Not tainted 2.6.24-rc6 #145
[<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
[<c43fda88>] mutex_lock_nested+0x98/0x2e0
[<c40c9a9e>] configfs_add_file+0x2e/0x70
[<c40c9b0c>] configfs_create_file+0x2c/0x40
[<c40ca639>] configfs_attach_item+0x139/0x220
[<c40ca734>] configfs_attach_group+0x14/0x140
[<c40ca7e9>] configfs_attach_group+0xc9/0x140
[<c40ca9f6>] 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/file.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index a3658f9..397cb50 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -320,7 +320,7 @@ int configfs_add_file(struct dentry * dir, const struct configfs_attribute * att
umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
int error = 0;

- mutex_lock(&dir->d_inode->i_mutex);
+ mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_NORMAL);
error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type);
mutex_unlock(&dir->d_inode->i_mutex);

--
1.5.3.6


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