linux-kernel - Re: [External] Re: [PATCH v2] ext4: make dioread

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Message-ID: <bc8f48ce-7280-c70a-db7d-825923f08b48@bytedance.com>
Date:   Fri, 17 Feb 2023 00:10:42 +0800
From:   hanjinke <hanjinke.666@...edance.com>
To:     "Ritesh Harjani (IBM)" <ritesh.list@...il.com>, tytso@....edu,
        adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com
Subject: Re: [External] Re: [PATCH v2] ext4: make dioread_nolock consistent in
 each mapping round



在 2023/2/16 下午9:13, Ritesh Harjani (IBM) 写道:
> Jinke Han <hanjinke.666@...edance.com> writes:
> 
>> From: Jinke Han <hanjinke.666@...edance.com>
>>
>> When disable and enable dioread_nolock by remount, we may see
>> dioread_lock in ext4_do_writepages while see dioread_nolock in
>> mpage_map_one_extent. This inconsistency may triger the warning
>> in ext4_add_complete_io when the io_end->handle is NULL. Although
>> this warning is harmless in most cases, there is still a risk of
>> insufficient log reservation in conversion of unwritten extents.
>>
> 
> Sorry, I haven't completely gone through the patch yet. But this idea of
> caching the initial value of mount parameter and passing it do different
> functions while an I/O request completes, is not looking right to me.
> 
> If that's the case shouldn't we disallow this mount option to change
> until all the outstanding I/O's are done or complete?
> Then we need not cache the value of dioread_nolock at the start of
> writepages and continue to pass it down in case it it changes.
> 
> Just my initial thoughts.
> 
> -ritesh
> 

Fair enough, thanks.