Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755962AbaBKU53 (ORCPT ); Tue, 11 Feb 2014 15:57:29 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:39631 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752736AbaBKTFU (ORCPT ); Tue, 11 Feb 2014 14:05:20 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mikulas Patocka , Mike Snitzer Subject: [PATCH 3.13 053/120] dm: wait until embedded kobject is released before destroying a device Date: Tue, 11 Feb 2014 11:04:54 -0800 Message-Id: <20140211184825.139553492@linuxfoundation.org> X-Mailer: git-send-email 1.8.5.1.163.gd7aced9 In-Reply-To: <20140211184823.492407127@linuxfoundation.org> References: <20140211184823.492407127@linuxfoundation.org> User-Agent: quilt/0.61-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mikulas Patocka commit be35f486108227e10fe5d96fd42fb2b344c59983 upstream. There may be other parts of the kernel holding a reference on the dm kobject. We must wait until all references are dropped before deallocating the mapped_device structure. The dm_kobject_release method signals that all references are dropped via completion. But dm_kobject_release doesn't free the kobject (which is embedded in the mapped_device structure). This is the sequence of operations: * when destroying a DM device, call kobject_put from dm_sysfs_exit * wait until all users stop using the kobject, when it happens the release method is called * the release method signals the completion and should return without delay * the dm device removal code that waits on the completion continues * the dm device removal code drops the dm_mod reference the device had * the dm device removal code frees the mapped_device structure that contains the kobject Using kobject this way should avoid the module unload race that was mentioned at the beginning of this thread: https://lkml.org/lkml/2014/1/4/83 Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-sysfs.c | 10 +++++++++- drivers/md/dm.c | 11 +++++++++++ drivers/md/dm.h | 2 ++ 3 files changed, 22 insertions(+), 1 deletion(-) --- a/drivers/md/dm-sysfs.c +++ b/drivers/md/dm-sysfs.c @@ -79,6 +79,11 @@ static const struct sysfs_ops dm_sysfs_o .show = dm_attr_show, }; +static void dm_kobject_release(struct kobject *kobj) +{ + complete(dm_get_completion_from_kobject(kobj)); +} + /* * dm kobject is embedded in mapped_device structure * no need to define release function here @@ -86,6 +91,7 @@ static const struct sysfs_ops dm_sysfs_o static struct kobj_type dm_ktype = { .sysfs_ops = &dm_sysfs_ops, .default_attrs = dm_attrs, + .release = dm_kobject_release, }; /* @@ -104,5 +110,7 @@ int dm_sysfs_init(struct mapped_device * */ void dm_sysfs_exit(struct mapped_device *md) { - kobject_put(dm_kobject(md)); + struct kobject *kobj = dm_kobject(md); + kobject_put(kobj); + wait_for_completion(dm_get_completion_from_kobject(kobj)); } --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -203,6 +203,9 @@ struct mapped_device { /* sysfs handle */ struct kobject kobj; + /* wait until the kobject is released */ + struct completion kobj_completion; + /* zero-length flush that will be cloned and submitted to targets */ struct bio flush_bio; @@ -2041,6 +2044,7 @@ static struct mapped_device *alloc_dev(i init_waitqueue_head(&md->wait); INIT_WORK(&md->work, dm_wq_work); init_waitqueue_head(&md->eventq); + init_completion(&md->kobj_completion); md->disk->major = _major; md->disk->first_minor = minor; @@ -2925,6 +2929,13 @@ struct mapped_device *dm_get_from_kobjec return md; } +struct completion *dm_get_completion_from_kobject(struct kobject *kobj) +{ + struct mapped_device *md = container_of(kobj, struct mapped_device, kobj); + + return &md->kobj_completion; +} + int dm_suspended_md(struct mapped_device *md) { return test_bit(DMF_SUSPENDED, &md->flags); --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -15,6 +15,7 @@ #include #include #include +#include #include "dm-stats.h" @@ -152,6 +153,7 @@ int dm_sysfs_init(struct mapped_device * void dm_sysfs_exit(struct mapped_device *md); struct kobject *dm_kobject(struct mapped_device *md); struct mapped_device *dm_get_from_kobject(struct kobject *kobj); +struct completion *dm_get_completion_from_kobject(struct kobject *kobj); /* * Targets for linear and striped mappings -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/