From: Luis Chamberlain <mcgrof@kernel.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: tj@kernel.org, gregkh@linuxfoundation.org,
akpm@linux-foundation.org, minchan@kernel.org, jeyu@kernel.org,
shuah@kernel.org, bvanassche@acm.org, dan.j.williams@intel.com,
joe@perches.com, tglx@linutronix.de, keescook@chromium.org,
rostedt@goodmis.org, linux-spdx@vger.kernel.org,
linux-doc@vger.kernel.org, linux-block@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate
Date: Thu, 14 Oct 2021 17:22:40 -0700 [thread overview]
Message-ID: <YWjJ0O7K+31Iz3ox@bombadil.infradead.org> (raw)
In-Reply-To: <YWjCpLUNPF3s4P2U@T590>
On Fri, Oct 15, 2021 at 07:52:04AM +0800, Ming Lei wrote:
> On Thu, Oct 14, 2021 at 01:24:32PM -0700, Luis Chamberlain wrote:
> > On Thu, Oct 14, 2021 at 10:11:46AM +0800, Ming Lei wrote:
> > > On Thu, Oct 14, 2021 at 09:55:48AM +0800, Ming Lei wrote:
> > > > On Mon, Sep 27, 2021 at 09:38:04AM -0700, Luis Chamberlain wrote:
> > >
> > > ...
> > >
> > > >
> > > > Hello Luis,
> > > >
> > > > Can you test the following patch and see if the issue can be addressed?
> > > >
> > > > Please see the idea from the inline comment.
> > > >
> > > > Also zram_index_mutex isn't needed in zram disk's store() compared with
> > > > your patch, then the deadlock issue you are addressing in this series can
> > > > be avoided.
> > > >
> > > >
> > > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > > > index fcaf2750f68f..3c17927d23a7 100644
> > > > --- a/drivers/block/zram/zram_drv.c
> > > > +++ b/drivers/block/zram/zram_drv.c
> > > > @@ -1985,11 +1985,17 @@ static int zram_remove(struct zram *zram)
> > > >
> > > > /* Make sure all the pending I/O are finished */
> > > > fsync_bdev(bdev);
> > > > - zram_reset_device(zram);
> > > >
> > > > pr_info("Removed device: %s\n", zram->disk->disk_name);
> > > >
> > > > del_gendisk(zram->disk);
> > > > +
> > > > + /*
> > > > + * reset device after gendisk is removed, so any change from sysfs
> > > > + * store won't come in, then we can really reset device here
> > > > + */
> > > > + zram_reset_device(zram);
> > > > +
> > > > blk_cleanup_disk(zram->disk);
> > > > kfree(zram);
> > > > return 0;
> > > > @@ -2073,7 +2079,12 @@ static int zram_remove_cb(int id, void *ptr, void *data)
> > > > static void destroy_devices(void)
> > > > {
> > > > class_unregister(&zram_control_class);
> > > > +
> > > > + /* hold the global lock so new device can't be added */
> > > > + mutex_lock(&zram_index_mutex);
> > > > idr_for_each(&zram_index_idr, &zram_remove_cb, NULL);
> > > > + mutex_unlock(&zram_index_mutex);
> > > > +
> > >
> > > Actually zram_index_mutex isn't needed when calling zram_remove_cb()
> > > since the zram-control sysfs interface has been removed, so userspace
> > > can't add new device any more, then the issue is supposed to be fixed
> > > by the following one line change, please test it:
> > >
> > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > > index fcaf2750f68f..96dd641de233 100644
> > > --- a/drivers/block/zram/zram_drv.c
> > > +++ b/drivers/block/zram/zram_drv.c
> > > @@ -1985,11 +1985,17 @@ static int zram_remove(struct zram *zram)
> > >
> > > /* Make sure all the pending I/O are finished */
> > > fsync_bdev(bdev);
> > > - zram_reset_device(zram);
> > >
> > > pr_info("Removed device: %s\n", zram->disk->disk_name);
> > >
> > > del_gendisk(zram->disk);
> > > +
> > > + /*
> > > + * reset device after gendisk is removed, so any change from sysfs
> > > + * store won't come in, then we can really reset device here
> > > + */
> > > + zram_reset_device(zram);
> > > +
> > > blk_cleanup_disk(zram->disk);
> > > kfree(zram);
> > > return 0;
> >
> > Sorry but nope, the cpu multistate issue is still present and we end up
> > eventually with page faults. I tried with both patches.
>
> In theory disksize_store() can't come in after del_gendisk() returns,
> then zram_reset_device() should cleanup everything, that is the issue
> you described in commit log.
>
> We need to understand the exact reason why there is still cpuhp node
> left, can you share us the exact steps for reproducing the issue?
> Otherwise we may have to trace and narrow down the reason.
See my commit log for my own fix for this issue.
Luis
next prev parent reply other threads:[~2021-10-15 0:23 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-27 16:37 [PATCH v8 00/12] syfs: generic deadlock fix with module removal Luis Chamberlain
2021-09-27 16:37 ` [PATCH v8 01/12] LICENSES: Add the copyleft-next-0.3.1 license Luis Chamberlain
[not found] ` <202110050907.35FBD2A1@keescook>
[not found] ` <YWR2ZrtzChamY1y4@bombadil.infradead.org>
2021-10-11 17:57 ` Kees Cook
2021-09-27 16:37 ` [PATCH v8 02/12] testing: use the copyleft-next-0.3.1 SPDX tag Luis Chamberlain
2021-10-05 16:11 ` Kees Cook
2021-09-27 16:37 ` [PATCH v8 03/12] selftests: add tests_sysfs module Luis Chamberlain
2021-10-05 14:16 ` Greg KH
2021-10-05 16:57 ` Tim.Bird
2021-10-11 17:40 ` Luis Chamberlain
2021-10-11 17:38 ` Luis Chamberlain
2021-10-07 14:23 ` Miroslav Benes
2021-10-11 19:11 ` Luis Chamberlain
[not found] ` <202110050912.3DF681ED@keescook>
2021-10-11 19:03 ` Luis Chamberlain
2021-09-27 16:37 ` [PATCH v8 04/12] kernfs: add initial failure injection support Luis Chamberlain
2021-10-05 19:47 ` Kees Cook
2021-10-11 20:44 ` Luis Chamberlain
2021-09-27 16:37 ` [PATCH v8 05/12] test_sysfs: add support to use kernfs failure injection Luis Chamberlain
2021-10-05 19:51 ` Kees Cook
2021-10-11 20:56 ` Luis Chamberlain
2021-09-27 16:37 ` [PATCH v8 06/12] kernel/module: add documentation for try_module_get() Luis Chamberlain
2021-10-05 19:58 ` Kees Cook
2021-10-11 21:16 ` Luis Chamberlain
2021-09-27 16:38 ` [PATCH v8 07/12] fs/kernfs/symlink.c: replace S_IRWXUGO with 0777 on kernfs_create_link() Luis Chamberlain
2021-10-05 19:59 ` Kees Cook
2021-09-27 16:38 ` [PATCH v8 08/12] fs/sysfs/dir.c: replace S_IRWXU|S_IRUGO|S_IXUGO with 0755 sysfs_create_dir_ns() Luis Chamberlain
2021-10-05 16:05 ` Kees Cook
2021-09-27 16:38 ` [PATCH v8 09/12] sysfs: fix deadlock race with module removal Luis Chamberlain
2021-10-05 9:24 ` Ming Lei
2021-10-11 21:25 ` Luis Chamberlain
2021-10-12 0:20 ` Ming Lei
2021-10-12 21:18 ` Luis Chamberlain
2021-10-13 1:07 ` Ming Lei
2021-10-13 12:35 ` Luis Chamberlain
2021-10-13 15:04 ` Ming Lei
2021-10-13 21:16 ` Luis Chamberlain
2021-10-05 20:50 ` Kees Cook
2021-10-11 22:26 ` Luis Chamberlain
2021-10-13 12:41 ` Luis Chamberlain
2021-09-27 16:38 ` [PATCH v8 10/12] test_sysfs: enable deadlock tests by default Luis Chamberlain
2021-09-27 16:38 ` [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate Luis Chamberlain
2021-10-05 20:55 ` Kees Cook
2021-10-11 18:27 ` Luis Chamberlain
2021-10-14 1:55 ` Ming Lei
2021-10-14 2:11 ` Ming Lei
2021-10-14 20:24 ` Luis Chamberlain
2021-10-14 23:52 ` Ming Lei
2021-10-15 0:22 ` Luis Chamberlain [this message]
2021-10-15 8:36 ` Ming Lei
2021-10-15 8:52 ` Greg KH
2021-10-15 17:31 ` Luis Chamberlain
2021-10-16 11:28 ` Ming Lei
2021-10-18 19:32 ` Luis Chamberlain
2021-10-19 2:34 ` Ming Lei
2021-10-19 6:23 ` Miroslav Benes
2021-10-19 9:23 ` Ming Lei
2021-10-20 6:43 ` Miroslav Benes
2021-10-20 7:49 ` Ming Lei
2021-10-20 8:19 ` Miroslav Benes
2021-10-20 8:28 ` Greg KH
2021-10-25 9:58 ` Miroslav Benes
2021-10-20 10:09 ` Ming Lei
2021-10-26 8:48 ` Petr Mladek
2021-10-26 15:37 ` Ming Lei
2021-10-26 17:01 ` Luis Chamberlain
2021-10-27 11:57 ` Miroslav Benes
2021-10-27 14:27 ` Luis Chamberlain
2021-11-02 15:24 ` Petr Mladek
2021-11-02 16:25 ` Luis Chamberlain
2021-11-03 0:01 ` Ming Lei
2021-11-03 12:44 ` Luis Chamberlain
2021-10-27 11:42 ` Miroslav Benes
2021-11-02 14:15 ` Petr Mladek
2021-11-02 14:51 ` Petr Mladek
2021-11-02 15:17 ` Ming Lei
2021-11-02 14:56 ` Ming Lei
2021-10-19 15:28 ` Luis Chamberlain
2021-10-19 16:29 ` Ming Lei
2021-10-19 19:36 ` Luis Chamberlain
2021-10-20 1:15 ` Ming Lei
2021-10-20 15:48 ` Luis Chamberlain
2021-10-21 0:39 ` Ming Lei
2021-10-21 17:18 ` Luis Chamberlain
2021-10-22 0:05 ` Ming Lei
2021-10-19 15:50 ` Luis Chamberlain
2021-10-19 16:25 ` Greg KH
2021-10-19 16:30 ` Luis Chamberlain
2021-10-19 17:28 ` Greg KH
2021-10-19 19:46 ` Luis Chamberlain
2021-10-19 16:39 ` Ming Lei
2021-10-19 19:38 ` Luis Chamberlain
2021-10-20 0:55 ` Ming Lei
2021-09-27 16:38 ` [PATCH v8 12/12] zram: use ATTRIBUTE_GROUPS to fix sysfs deadlock module removal Luis Chamberlain
2021-10-05 20:57 ` Kees Cook
2021-10-11 18:28 ` Luis Chamberlain
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