[PATCH 14/19] driver core: set PF_FSTRANS while holding gdp_mutex

NeilBrown
2014-04-16T04:19:33Z

lockdep reports a locking chain:

sk_lock-AF_INET --> rtnl_mutex --> gdp_mutex

As sk_lock can be needed for memory reclaim (when loop-back NFS is in
use at least), any memory allocation under gdp_mutex needs to
be protected by PF_FSTRANS.

The path frome rtnl_mutex to gdp_mutex is

[<ffffffff81841ecc>] get_device_parent+0x4c/0x1f0
[<ffffffff81842496>] device_add+0xe6/0x610
[<ffffffff81ac5f2a>] netdev_register_kobject+0x7a/0x130
[<ffffffff81aaf5d4>] register_netdevice+0x354/0x550
[<ffffffff81aaf7e5>] register_netdev+0x15/0x30

Signed-off-by: NeilBrown <neilb@suse.de>
---
drivers/base/core.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 2b567177ef78..1a2735237650 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -750,6 +750,7 @@ static struct kobject *get_device_parent(struct device *dev,
struct kobject *kobj = NULL;
struct kobject *parent_kobj;
struct kobject *k;
+ unsigned int pflags;

#ifdef CONFIG_BLOCK
/* block disks show up in /sys/block */
@@ -788,7 +789,9 @@ static struct kobject *get_device_parent(struct device *dev,
}

/* or create a new class-directory at the parent device */
+ current_set_flags_nested(&pflags, PF_FSTRANS);
k = class_dir_create_and_add(dev->class, parent_kobj);
+ current_restore_flags_nested(&pflags, PF_FSTRANS);
/* do not emit an uevent for this simple "glue" directory */
mutex_unlock(&gdp_mutex);
return k;