From: Qu Wenruo <quwenruo.btrfs@gmx.com>
To: fdmanana@gmail.com
Cc: Qu Wenruo <wqu@suse.com>,
linux-btrfs <linux-btrfs@vger.kernel.org>,
Filipe Manana <fdmanana@suse.com>
Subject: Re: [PATCH] btrfs: scrub: Require mandatory block group RO for dev-replace
Date: Thu, 23 Jan 2020 21:57:53 +0800 [thread overview]
Message-ID: <e2002d7e-daba-9fcb-0442-2feddfa7ec30@gmx.com> (raw)
In-Reply-To: <CAL3q7H5NudsNQZo+W1mJ26VxFTrowpqAH7soE0j3F2GTygae8w@mail.gmail.com>
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On 2020/1/23 下午9:49, Filipe Manana wrote:
[...]
>> This btrfs_wait_nocow_writers() is not just triggering ordered extents
>> for nocow.
>> It waits for the nocow_writers count decreased to 0 for that block group.
>>
>> Since we have already marked the block group RO, no new nocow writers
>> can happen, thus that counter can only decrease, no way to increase.
>>
>> There are several cases involved:
>> - NoCOW Write back happens before bg RO
>> It will increase cache->nocow_writers counter, and decrease the
>> counter after finish_oredered_io().
>
> Nop. nocow_writers is decremented after creating the ordered extent
> when starting writeback (at run_delalloc_nocow) - not when completing
> the ordered extent (at btrfs_finish_ordered_io()).
Oh, right. The dec part still happens in run_delalloc_nocow().
So the wait_ordered_roots() call is still needed.
Thanks,
Qu
> Same applies direct IO.
>
> Thanks
>
>>>
>>
>
>
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next prev parent reply other threads:[~2020-01-23 13:58 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-23 7:37 [PATCH] btrfs: scrub: Require mandatory block group RO for dev-replace Qu Wenruo
2020-01-23 12:06 ` Filipe Manana
2020-01-23 12:28 ` Qu WenRuo
2020-01-23 13:39 ` Qu Wenruo
2020-01-23 13:49 ` Filipe Manana
2020-01-23 13:57 ` Qu Wenruo [this message]
2020-01-23 16:40 ` David Sterba
2020-01-23 23:58 ` Qu Wenruo
-- strict thread matches above, loose matches on Subject: below --
2020-01-23 23:58 Qu Wenruo
2020-01-24 9:24 ` Filipe Manana
2020-01-24 13:40 ` David Sterba
2020-01-24 14:44 ` David Sterba
2020-01-24 16:28 ` Filipe Manana
2020-01-25 0:36 ` Qu Wenruo
2020-01-25 0:48 ` Qu Wenruo
2020-01-25 11:35 ` David Sterba
2020-01-25 12:09 ` Qu WenRuo
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