diff options
author | Mikulas Patocka <mpatocka@redhat.com> | 2014-01-07 04:01:22 (GMT) |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-02-13 21:50:17 (GMT) |
commit | 7cc8d93049998a20834b50fd4a7bd0f14feb59b3 (patch) | |
tree | 3f0322b9925517ea2753e898c13e041e5373909b | |
parent | 465c661f3e4957f1014cbc3e3dcdfd542a7b3c7a (diff) | |
download | linux-fsl-qoriq-7cc8d93049998a20834b50fd4a7bd0f14feb59b3.tar.xz |
dm: wait until embedded kobject is released before destroying a device
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 <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | drivers/md/dm-sysfs.c | 10 | ||||
-rw-r--r-- | drivers/md/dm.c | 11 | ||||
-rw-r--r-- | drivers/md/dm.h | 2 |
3 files changed, 22 insertions, 1 deletions
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 b3e26c7..c157959 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -197,6 +197,9 @@ 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; @@ -2005,6 +2008,7 @@ 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; @@ -2889,6 +2893,13 @@ 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 1d1ad7b..a3406e0 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -15,6 +15,7 @@ #include <linux/list.h> #include <linux/blkdev.h> #include <linux/hdreg.h> +#include <linux/completion.h> #include "dm-stats.h" @@ -142,6 +143,7 @@ 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 |