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Subject[PATCH v3.13-rc1 1/2] sysfs: handle duplicate removal attempts in sysfs_remove_group()
Hello, Greg.

These are two patches to fix sysfs bugs which are present in rc1 and
posted previously. Both deal with spurious triggering of warnings.
The patches are available in the following git branch.

git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git review-sysfs-fixes

The original patches are

http://lkml.kernel.org/g/1384866598-19716-1-git-send-email-mika.westerberg@linux.intel.com
http://lkml.kernel.org/g/20131117021736.GA9302@mtj.dyndns.org

I'll base further sysfs/kernfs patches on top of the above branch.

Thanks!
------- 8< -------
From a69cc96d8c434c6cb64847f37caa890af705fc5c Mon Sep 17 00:00:00 2001
From: Mika Westerberg <mika.westerberg@linux.intel.com>
Date: Wed, 20 Nov 2013 11:56:35 +0200

Commit bcdde7e221a8 (sysfs: make __sysfs_remove_dir() recursive) changed
the behavior so that directory removals will be done recursively. This
means that the sysfs group might already be removed if its parent directory
has been removed.

The current code outputs warnings similar to following log snippet when it
detects that there is no group for the given kobject:

WARNING: CPU: 0 PID: 4 at fs/sysfs/group.c:214 sysfs_remove_group+0xc6/0xd0()
sysfs group ffffffff81c6f1e0 not found for kobject 'host7'
Modules linked in:
CPU: 0 PID: 4 Comm: kworker/0:0 Not tainted 3.12.0+ #13
Hardware name: /D33217CK, BIOS GKPPT10H.86A.0042.2013.0422.1439 04/22/2013
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
0000000000000009 ffff8801002459b0 ffffffff817daab1 ffff8801002459f8
ffff8801002459e8 ffffffff810436b8 0000000000000000 ffffffff81c6f1e0
ffff88006d440358 ffff88006d440188 ffff88006e8b4c28 ffff880100245a48
Call Trace:
[<ffffffff817daab1>] dump_stack+0x45/0x56
[<ffffffff810436b8>] warn_slowpath_common+0x78/0xa0
[<ffffffff81043727>] warn_slowpath_fmt+0x47/0x50
[<ffffffff811ad319>] ? sysfs_get_dirent_ns+0x49/0x70
[<ffffffff811ae526>] sysfs_remove_group+0xc6/0xd0
[<ffffffff81432f7e>] dpm_sysfs_remove+0x3e/0x50
[<ffffffff8142a0d0>] device_del+0x40/0x1b0
[<ffffffff8142a24d>] device_unregister+0xd/0x20
[<ffffffff8144131a>] scsi_remove_host+0xba/0x110
[<ffffffff8145f526>] ata_host_detach+0xc6/0x100
[<ffffffff8145f578>] ata_pci_remove_one+0x18/0x20
[<ffffffff812e8f48>] pci_device_remove+0x28/0x60
[<ffffffff8142d854>] __device_release_driver+0x64/0xd0
[<ffffffff8142d8de>] device_release_driver+0x1e/0x30
[<ffffffff8142d257>] bus_remove_device+0xf7/0x140
[<ffffffff8142a1b1>] device_del+0x121/0x1b0
[<ffffffff812e43d4>] pci_stop_bus_device+0x94/0xa0
[<ffffffff812e437b>] pci_stop_bus_device+0x3b/0xa0
[<ffffffff812e437b>] pci_stop_bus_device+0x3b/0xa0
[<ffffffff812e44dd>] pci_stop_and_remove_bus_device+0xd/0x20
[<ffffffff812fc743>] trim_stale_devices+0x73/0xe0
[<ffffffff812fc78b>] trim_stale_devices+0xbb/0xe0
[<ffffffff812fc78b>] trim_stale_devices+0xbb/0xe0
[<ffffffff812fcb6e>] acpiphp_check_bridge+0x7e/0xd0
[<ffffffff812fd90d>] hotplug_event+0xcd/0x160
[<ffffffff812fd9c5>] hotplug_event_work+0x25/0x60
[<ffffffff81316749>] acpi_hotplug_work_fn+0x17/0x22
[<ffffffff8105cf3a>] process_one_work+0x17a/0x430
[<ffffffff8105db29>] worker_thread+0x119/0x390
[<ffffffff8105da10>] ? manage_workers.isra.25+0x2a0/0x2a0
[<ffffffff81063a5d>] kthread+0xcd/0xf0
[<ffffffff81063990>] ? kthread_create_on_node+0x180/0x180
[<ffffffff817eb33c>] ret_from_fork+0x7c/0xb0
[<ffffffff81063990>] ? kthread_create_on_node+0x180/0x180

On this particular machine I see ~16 of these message during Thunderbolt
hot-unplug.

Fix this in similar way that was done for sysfs_remove_one() by checking
if the parent directory has already been removed and bailing out early.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Tejun Heo <tj@kernel.org>
---
fs/sysfs/group.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
index 1898a10..3796afd 100644
--- a/fs/sysfs/group.c
+++ b/fs/sysfs/group.c
@@ -206,6 +206,15 @@ void sysfs_remove_group(struct kobject *kobj,
struct sysfs_dirent *dir_sd = kobj->sd;
struct sysfs_dirent *sd;

+ /*
+ * Sysfs directories are now removed recursively by
+ * sysfs_remove_dir(). This means that the function can be called
+ * for a group whose sysfs entry is already removed. In that case
+ * all its groups are guaranteed to be already removed.
+ */
+ if (dir_sd->s_flags & SYSFS_FLAG_REMOVED)
+ return;
+
if (grp->name) {
sd = sysfs_get_dirent(dir_sd, grp->name);
if (!sd) {
--
1.8.4.2


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