Received-SPF: pass (google.com: domain of linux-kernel+bounces-199253-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Subject: Re: [RFC PATCH v4 5/8] xfs: refactor the truncating order
To: "Darrick J. Wong" <djwong@kernel.org>,
 Christoph Hellwig <hch@infradead.org>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
 linux-kernel@vger.kernel.org, brauner@kernel.org, david@fromorbit.com,
 chandanbabu@kernel.org, jack@suse.cz, willy@infradead.org,
 yi.zhang@huawei.com, chengzhihao1@huawei.com, yukuai3@huawei.com
References: <20240529095206.2568162-1-yi.zhang@huaweicloud.com>
 <20240529095206.2568162-6-yi.zhang@huaweicloud.com>
 <ZlnRODP_b8bhXOEE@infradead.org> <20240531152732.GM52987@frogsfrogsfrogs>
From: Zhang Yi <yi.zhang@huaweicloud.com>
Message-ID: <de2c345e-6892-f3c1-09a9-cdf5991cca7e@huaweicloud.com>
Date: Mon, 3 Jun 2024 21:51:16 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.12.0
Precedence: bulk
MIME-Version: 1.0
In-Reply-To: <20240531152732.GM52987@frogsfrogsfrogs>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit

On 2024/5/31 23:27, Darrick J. Wong wrote:
> On Fri, May 31, 2024 at 06:31:36AM -0700, Christoph Hellwig wrote:
>>> +	write_back = newsize > ip->i_disk_size && oldsize != ip->i_disk_size;
>>
>> Maybe need_writeback would be a better name for the variable?  Also no
>> need to initialize it to false at declaration time if it is
>> unconditionally set here.
> 
> This variable captures whether or not we need to write dirty file tail
> data because we're extending the ondisk EOF, right?
> 
> I don't really like long names like any good 1980s C programmer, but
> maybe we should name this something like "extending_ondisk_eof"?
> 
> 	if (newsize > ip->i_disk_size && oldsize != ip->i_disk_size)
> 		extending_ondisk_eof = true;
> 
> 	...
> 
> 	if (did_zeroing || extending_ondisk_eof)
> 		filemap_write_and_wait_range(...);
> 
> Hm?

Sure, this name looks better.

> 
>>> +		/*
>>> +		 * Updating i_size after writing back to make sure the zeroed
>>> +		 * blocks could been written out, and drop all the page cache
>>> +		 * range that beyond blocksize aligned new EOF block.
>>> +		 *
>>> +		 * We've already locked out new page faults, so now we can
>>> +		 * safely remove pages from the page cache knowing they won't
>>> +		 * get refaulted until we drop the XFS_MMAP_EXCL lock after the
> 
> And can we correct the comment here too?
> 
> "...until we drop XFS_MMAPLOCK_EXCL after the extent manipulations..."
> 

Sure,

> --D
> 
>>> +		 * extent manipulations are complete.
>>> +		 */
>>> +		i_size_write(inode, newsize);
>>> +		truncate_pagecache(inode, roundup_64(newsize, blocksize));
>>
>> Any reason this open codes truncate_setsize()?
>>

It's not equal to open codes truncate_setsize(), please look the truncate
start pos is aligned to rtextsize for realtime inode, we only drop page
cache that beyond the new aligned EOF block.

Thanks,
Yi.