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author | 2014-01-06 23:01:22 -0500 | |
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committer | 2014-01-07 21:01:43 -0500 | |
commit | be35f486108227e10fe5d96fd42fb2b344c59983 (patch) | |
tree | 9cfaef139722da4118b4fcd906eb1196d9577b23 /drivers/md/dm.h | |
parent | dm: remove pointless kobject comparison in dm_get_from_kobject (diff) | |
download | linux-be35f486108227e10fe5d96fd42fb2b344c59983.tar.gz linux-be35f486108227e10fe5d96fd42fb2b344c59983.tar.bz2 linux-be35f486108227e10fe5d96fd42fb2b344c59983.zip |
dm: wait until embedded kobject is released before destroying a device
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
Diffstat (limited to 'drivers/md/dm.h')
-rw-r--r-- | drivers/md/dm.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/md/dm.h b/drivers/md/dm.h index c57ba550f69e..1ab2028559ca 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" @@ -152,6 +153,7 @@ 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 |