From: Heming Zhao <email@example.com>
To: Joe Thornber <firstname.lastname@example.org>,
LVM general discussion and development <email@example.com>
Cc: David Teigland <firstname.lastname@example.org>
Subject: Re: [linux-lvm] resend patch - bcache may mistakenly write data to another disk when writes error
Date: Thu, 24 Oct 2019 03:13:53 +0000 [thread overview]
Message-ID: <email@example.com> (raw)
Please see my comments in below. Thanks.
(+joe, pls ignore previous mail. It is very wired: in last mail, Thunderbird reply all not include joe.)
On 10/24/19 5:31 AM, Joe Thornber wrote:
> On Tue, Oct 22, 2019 at 09:47:32AM +0000, Heming Zhao wrote:
>> Hello List & David,
>> This patch is responsible for legacy mail:
>> [linux-lvm] pvresize will cause a meta-data corruption with error message "Error writing device at 4096 length 512"
>> I had send it to our customer, the code ran as expected. I think this code is enough to fix this issue.
>> ------(patch for branch stable-2.02) ----------
>> From d0d77d0bdad6136c792c9664444d73dd47b809cb Mon Sep 17 00:00:00 2001
>> From: Zhao Heming <firstname.lastname@example.org>
>> Date: Tue, 22 Oct 2019 17:22:17 +0800
>> Subject: [PATCH] bcache may mistakenly write data to another disk when writes
>> When bcache write data error, the errored fd and its data is saved in
>> cache->errored, then this fd is closed. Later lvm will reuse this
>> closed fd to new opened devs, but the fd related data still in
>> cache->errored and flags with BF_DIRTY. It make the data may mistakenly
>> write to another disk.
> I think real issue here is that the flush fails, and the error path for that
> calls invalidate dev, which also fails, but that return value is not checked.
> The fd is subsequently closed, and reopened with data still in the cache.
First fail is in bcache_flush, then bcache_invalidate_fd does nothing because the data
in cache->errored, which not belongs to dirty & clean list. Then the data mistakenly
move from cache->errored into cache->dirty by "bcache_get => _lookup_or_read_block"
(because the data holds BF_DIRTY flag).
> So I think the correct fix is to have a variant of invalidate, that doesn't
> bother retrying the IO, and just throws away the dirty data. bcache_abort()?
> This should be called when the flush() fails.
Currently lvm2 calls bcache_invalidate_fd when flush fails. So I add abort action
in invalidate(). You can see the handle errored list codes in invalidate(). It's
not necessary to add a new func bcache_abort().
So IMO both bcache_flush & bcache_invalidate_fd have bug.
- bcache_flush should do more error/fail check.
- invalidate should do abort job.
BTW, yesterday I found my patch a mistake, it overwrites some correct code. And I
only sent it to David with V2 patch.
> - Joe
> linux-lvm mailing list
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
next prev parent reply other threads:[~2019-10-24 3:13 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-22 9:47 [linux-lvm] resend patch - bcache may mistakenly write data to another disk when writes error Heming Zhao
2019-10-23 21:31 ` Joe Thornber
2019-10-24 3:06 ` Heming Zhao
2019-10-28 15:43 ` Joe Thornber
2019-10-29 5:07 ` Heming Zhao
2019-10-29 9:46 ` Heming Zhao
2019-10-29 11:05 ` Joe Thornber
2019-10-29 11:47 ` Heming Zhao
2019-10-29 14:41 ` Joe Thornber
2019-10-29 11:01 ` Joe Thornber
2019-10-29 11:41 ` Heming Zhao
2019-10-24 3:13 ` Heming Zhao [this message]
2019-10-28 8:38 ` Heming Zhao
[not found] <email@example.com>
[not found] ` <firstname.lastname@example.org>
2019-11-12 15:21 ` David Teigland
[not found] ` <email@example.com>
2019-11-13 15:41 ` David Teigland
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