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Subject: Re: [PATCH 1/7] fs/writeback: avoid to writeback non-expired inode in
 kupdate writeback
From: Kemeng Shi <shikemeng@huaweicloud.com>
To: Tim Chen <tim.c.chen@linux.intel.com>, viro@zeniv.linux.org.uk,
 brauner@kernel.org, jack@suse.cz
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20240208172024.23625-1-shikemeng@huaweicloud.com>
 <20240208172024.23625-2-shikemeng@huaweicloud.com>
 <ba75294dfb5bf4dd046d54de6c3e57698592dacc.camel@linux.intel.com>
 <4364e9bc-2d29-120d-4837-7f5620585508@huaweicloud.com>
Message-ID: <64ceb2b1-a120-dcf1-0e5f-033033b47685@huaweicloud.com>
Date: Wed, 28 Feb 2024 09:46:18 +0800
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on 2/18/2024 10:01 AM, Kemeng Shi wrote:
> 
> 
> on 2/9/2024 2:29 AM, Tim Chen wrote:
>> On Fri, 2024-02-09 at 01:20 +0800, Kemeng Shi wrote:
>>>
>>>  
>>> +static void filter_expired_io(struct bdi_writeback *wb)
>>> +{
>>> +	struct inode *inode, *tmp;
>>> +	unsigned long expired_jiffies = jiffies -
>>> +		msecs_to_jiffies(dirty_expire_interval * 10);
>>
>> We have kupdate trigger time hard coded with a factor of 10 to expire interval here.
>> The kupdate trigger time "mssecs_to_jiffies(dirty_expire_interval * 10)" is
>> also used in wb_writeback().  It will be better to have a macro or #define
>> to encapsulate the trigger time so if for any reason we need
>> to tune the trigger time, we just need to change it at one place.
> Hi Tim. Sorry for the late reply, I was on vacation these days.
> I agree it's better to have a macro and I will add it in next version.
> Thanks!
Hi Tim,
After a deep look, I plan to set dirty_expire_interval in jiffies within sysctl
handler. Then we could use dirty_expire_interval directly instead of
"mssecs_to_jiffies(dirty_expire_interval * 10)" and macro is not needed.
Similar, dirty_writeback_interval and dirtytime_expire_interval could be set in
jiffies to remove repeat convertion from centisecs to jiffies. I will submit a
new series to do this if no one is against this.
Thanks!
>>
>> Tim
>>
>>> +
>>> +	spin_lock(&wb->list_lock);
>>> +	list_for_each_entry_safe(inode, tmp, &wb->b_io, i_io_list)
>>> +		if (inode_dirtied_after(inode, expired_jiffies))
>>> +			redirty_tail(inode, wb);
>>> +
>>> +	list_for_each_entry_safe(inode, tmp, &wb->b_more_io, i_io_list)
>>> +		if (inode_dirtied_after(inode, expired_jiffies))
>>> +			redirty_tail(inode, wb);
>>> +	spin_unlock(&wb->list_lock);
>>> +}
>>> +
>>>  /*
>>>   * Explicit flushing or periodic writeback of "old" data.
>>>   *
>>> @@ -2070,6 +2087,9 @@ static long wb_writeback(struct bdi_writeback *wb,
>>>  	long progress;
>>>  	struct blk_plug plug;
>>>  
>>> +	if (work->for_kupdate)
>>> +		filter_expired_io(wb);
>>> +
>>>  	blk_start_plug(&plug);
>>>  	for (;;) {
>>>  		/*
>>