From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754935AbaBGMzO (ORCPT ); Fri, 7 Feb 2014 07:55:14 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:41850 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754760AbaBGLt7 (ORCPT ); Fri, 7 Feb 2014 06:49:59 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Mikulas Patocka , Mike Snitzer , Luis Henriques Subject: [PATCH 3.11 096/233] dm: wait until embedded kobject is released before destroying a device Date: Fri, 7 Feb 2014 11:45:15 +0000 Message-Id: <1391773652-25214-97-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1391773652-25214-1-git-send-email-luis.henriques@canonical.com> References: <1391773652-25214-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.11.10.4 -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: Luis Henriques --- drivers/md/dm-sysfs.c | 10 +++++++++- drivers/md/dm.c | 11 +++++++++++ drivers/md/dm.h | 2 ++ 3 files changed, 22 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-sysfs.c b/drivers/md/dm-sysfs.c index 84d2b91..e0cc5d6 100644 --- a/drivers/md/dm-sysfs.c +++ b/drivers/md/dm-sysfs.c @@ -79,6 +79,11 @@ static const struct sysfs_ops dm_sysfs_ops = { .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_ops = { 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 *md) */ 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)); } diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 995e1fc..0cc1449 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -196,6 +196,9 @@ 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; }; @@ -1936,6 +1939,7 @@ static struct mapped_device *alloc_dev(int minor) 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; @@ -2784,6 +2788,13 @@ struct mapped_device *dm_get_from_kobject(struct kobject *kobj) 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); diff --git a/drivers/md/dm.h b/drivers/md/dm.h index 45b97da..66cfb7d 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -15,6 +15,7 @@ #include #include #include +#include /* * Suspend feature flags @@ -129,6 +130,7 @@ int dm_sysfs_init(struct mapped_device *md); 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 -- 1.8.3.2