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be35f48610
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 <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org
116 lines
2.4 KiB
C
116 lines
2.4 KiB
C
/*
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* Copyright (C) 2008 Red Hat, Inc. All rights reserved.
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*
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* This file is released under the GPL.
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*/
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#include <linux/sysfs.h>
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#include <linux/dm-ioctl.h>
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#include "dm.h"
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struct dm_sysfs_attr {
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struct attribute attr;
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ssize_t (*show)(struct mapped_device *, char *);
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ssize_t (*store)(struct mapped_device *, char *);
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};
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#define DM_ATTR_RO(_name) \
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struct dm_sysfs_attr dm_attr_##_name = \
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__ATTR(_name, S_IRUGO, dm_attr_##_name##_show, NULL)
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static ssize_t dm_attr_show(struct kobject *kobj, struct attribute *attr,
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char *page)
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{
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struct dm_sysfs_attr *dm_attr;
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struct mapped_device *md;
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ssize_t ret;
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dm_attr = container_of(attr, struct dm_sysfs_attr, attr);
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if (!dm_attr->show)
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return -EIO;
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md = dm_get_from_kobject(kobj);
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if (!md)
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return -EINVAL;
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ret = dm_attr->show(md, page);
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dm_put(md);
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return ret;
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}
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static ssize_t dm_attr_name_show(struct mapped_device *md, char *buf)
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{
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if (dm_copy_name_and_uuid(md, buf, NULL))
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return -EIO;
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strcat(buf, "\n");
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return strlen(buf);
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}
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static ssize_t dm_attr_uuid_show(struct mapped_device *md, char *buf)
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{
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if (dm_copy_name_and_uuid(md, NULL, buf))
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return -EIO;
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strcat(buf, "\n");
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return strlen(buf);
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}
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static ssize_t dm_attr_suspended_show(struct mapped_device *md, char *buf)
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{
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sprintf(buf, "%d\n", dm_suspended_md(md));
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return strlen(buf);
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}
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static DM_ATTR_RO(name);
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static DM_ATTR_RO(uuid);
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static DM_ATTR_RO(suspended);
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static struct attribute *dm_attrs[] = {
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&dm_attr_name.attr,
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&dm_attr_uuid.attr,
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&dm_attr_suspended.attr,
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NULL,
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};
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static const struct sysfs_ops dm_sysfs_ops = {
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.show = dm_attr_show,
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};
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static void dm_kobject_release(struct kobject *kobj)
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{
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complete(dm_get_completion_from_kobject(kobj));
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}
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/*
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* dm kobject is embedded in mapped_device structure
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* no need to define release function here
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*/
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static struct kobj_type dm_ktype = {
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.sysfs_ops = &dm_sysfs_ops,
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.default_attrs = dm_attrs,
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.release = dm_kobject_release,
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};
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/*
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* Initialize kobj
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* because nobody using md yet, no need to call explicit dm_get/put
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*/
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int dm_sysfs_init(struct mapped_device *md)
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{
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return kobject_init_and_add(dm_kobject(md), &dm_ktype,
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&disk_to_dev(dm_disk(md))->kobj,
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"%s", "dm");
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}
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/*
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* Remove kobj, called after all references removed
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*/
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void dm_sysfs_exit(struct mapped_device *md)
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{
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struct kobject *kobj = dm_kobject(md);
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kobject_put(kobj);
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wait_for_completion(dm_get_completion_from_kobject(kobj));
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}
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