linux-kernel - [PATCH 14/19] driver core: set PF_FSTRANS while holding gdp

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Message-ID: <20140416040336.10604.223.stgit@notabene.brown>
Date:	Wed, 16 Apr 2014 14:03:36 +1000
From:	NeilBrown <neilb@...e.de>
To:	linux-mm@...ck.org, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	xfs@....sgi.com
Subject: [PATCH 14/19] driver core: set PF_FSTRANS while holding gdp_mutex

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@...e.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;


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