From: Helen Koike <helen.koike@collabora.com>
To: Mike Snitzer <snitzer@redhat.com>
Cc: dm-devel@redhat.com, kernel@collabora.com,
linux-kernel@vger.kernel.org, Alasdair Kergon <agk@redhat.com>
Subject: Re: dm ioctl: fix hang in early create error condition
Date: Wed, 15 May 2019 13:12:03 -0300 [thread overview]
Message-ID: <78dda04b-925f-49eb-f88a-6d940bcc4754@collabora.com> (raw)
In-Reply-To: <20190514013716.GA10260@lobo>
Hi,
On 5/13/19 10:37 PM, Mike Snitzer wrote:
> On Mon, May 13 2019 at 3:25P -0400,
> Helen Koike <helen.koike@collabora.com> wrote:
>
>> The dm_early_create() function (which deals with "dm-mod.create=" kernel
>> command line option) calls dm_hash_insert() who gets an extra reference
>> to the md object.
>>
>> In case of failure, this reference wasn't being released, causing
>> dm_destroy() to hang, thus hanging the whole boot process.
>>
>> Fix this by calling __hash_remove() in the error path.
>>
>> Fixes: 6bbc923dfcf57d ("dm: add support to directly boot to a mapped device")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Helen Koike <helen.koike@collabora.com>
>>
>> ---
>> Hi,
>>
>> I tested this patch by adding a new test case in the following test
>> script:
>>
>> https://gitlab.collabora.com/koike/dm-cmdline-test/commit/d2d7a0ee4a49931cdb59f08a837b516c2d5d743d
>>
>> This test was failing, but with this patch it works correctly.
>>
>> Thanks
>> Helen
>
> Thanks for the patch but I'd prefer the following simpler fix. What do
> you think?
>
> That said, I can provide a follow-on patch (inspired by the patch you
> provided) that encourages more code sharing between dm_early_create()
> and dev_create() by factoring out __dev_create().
Sounds great.
>
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index c740153b4e52..0eb0b462c736 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -2117,6 +2117,7 @@ int __init dm_early_create(struct dm_ioctl *dmi,
> err_destroy_table:
> dm_table_destroy(t);
> err_destroy_dm:
> + (void) __hash_remove(__find_device_hash_cell(dmi));
> dm_put(md);
> dm_destroy(md);
> return r;
>
This doesn't really work for two reasons:
1) __find_device_hash_cell() requires a mutual exclusivity between name,
uuid and dev. In dm_early_create(), dmi can have more then one of these.
2) I can fix (1) by calling __get_name_cell(), as the name is mandatory
anyway, but this function also grabs another reference to the md object,
so I need to add an extra dm_put(md) there:
err_destroy_table:
dm_table_destroy(t);
+err_hash_remove:
+ (void) __hash_remove(__get_name_cell(dmi->name));
+ dm_put(md);
err_destroy_dm:
dm_put(md);
dm_destroy(md);
What do you think? Is this ok?
Thanks
Helen
next prev parent reply other threads:[~2019-05-15 16:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-13 19:25 [PATCH] dm ioctl: fix hang in early create error condition Helen Koike
2019-05-14 1:37 ` Mike Snitzer
2019-05-15 16:12 ` Helen Koike [this message]
2019-05-15 16:20 ` Mike Snitzer
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