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dm: use noio when sending kobject event 

kobject_uevent may allocate memory and it may be called while there are dm
devices suspended. The allocation may recurse into a suspended device,
causing a deadlock. We must set the noio flag when sending a uevent.

The observed deadlock was reported here:
https://www.redhat.com/archives/dm-devel/2020-March/msg00025.html

Reported-by: Khazhismel Kumykov <khazhy@google.com>
Reported-by: Tahsin Erdogan <tahsin@google.com>
Reported-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
alistair/sunxi64-5.8
Mikulas Patocka 2020-07-08 12:25:20 -04:00 committed by Mike Snitzer
parent 174364f6a8
commit 6958c1c640
1 changed files with 12 additions and 3 deletions
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15
drivers/md/dm.c
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@ -12,6 +12,7 @@
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/sched/mm.h>
#include <linux/sched/signal.h>
#include <linux/blkpg.h>
#include <linux/bio.h>
@ -2939,17 +2940,25 @@ EXPORT_SYMBOL_GPL(dm_internal_resume_fast);
int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
unsigned cookie)
{
int r;
unsigned noio_flag;
char udev_cookie[DM_COOKIE_LENGTH];
char *envp[] = { udev_cookie, NULL };
noio_flag = memalloc_noio_save();
if (!cookie)
return kobject_uevent(&disk_to_dev(md->disk)->kobj, action);
r = kobject_uevent(&disk_to_dev(md->disk)->kobj, action);
else {
snprintf(udev_cookie, DM_COOKIE_LENGTH, "%s=%u",
DM_COOKIE_ENV_VAR_NAME, cookie);
return kobject_uevent_env(&disk_to_dev(md->disk)->kobj,
action, envp);
r = kobject_uevent_env(&disk_to_dev(md->disk)->kobj,
action, envp);
}
memalloc_noio_restore(noio_flag);
return r;
}
uint32_t dm_next_uevent_seq(struct mapped_device *md)