Re: [f2fs-dev] [PATCH 6/9] f2fs: zstd: Switch to the zstd-1.4.6 API

From: Chao Yu <yuchao0@huawei.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Johannes Weiner <jweiner@fb.com>,
	Nick Terrell <nickrterrell@gmail.com>, Yann Collet <cyan@fb.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-f2fs-devel@lists.sourceforge.net"
	<linux-f2fs-devel@lists.sourceforge.net>,
	Petr Malat <oss@malat.biz>, Chris Mason <clm@fb.com>,
	Nick Terrell <terrelln@fb.com>, Kernel Team <Kernel-team@fb.com>,
	Niket Agarwal <niketa@fb.com>
Subject: Re: [f2fs-dev] [PATCH 6/9] f2fs: zstd: Switch to the zstd-1.4.6 API
Date: Fri, 18 Sep 2020 10:58:35 +0800	[thread overview]
Message-ID: <6eb268c8-7276-5859-e5b0-ce0a541e27e7@huawei.com> (raw)
In-Reply-To: <20200918025627.GA3518637@gmail.com>

On 2020/9/18 10:56, Eric Biggers wrote:
> On Fri, Sep 18, 2020 at 09:47:32AM +0800, Chao Yu wrote:
>> Ah, I got it.
>>
>> Step of enabling compressed inode is not correct, we should touch an empty
>> file, and then use 'chattr +c' on that file to enable compression, otherwise
>> the race condition could be complicated to handle. So we need below diff to
>> disallow setting compression flag on an non-empty file:
>>
>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>> index 8a422400e824..b462db7898fd 100644
>> --- a/fs/f2fs/file.c
>> +++ b/fs/f2fs/file.c
>> @@ -1836,6 +1836,8 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
>>   		if (iflags & F2FS_COMPR_FL) {
>>   			if (!f2fs_may_compress(inode))
>>   				return -EINVAL;
>> +			if (get_dirty_pages(inode) || fi->i_compr_blocks)
>> +				return  -EINVAL;
>>
>>   			set_compress_context(inode);
>>   		}
> 
> Why not:
> 
> 	if (inode->i_size)
> 		return -EINVAL;

Yeah, I noticed that after replying this email, I've prepared the new patch
which including the i_size check.

Thanks for noticing this.

Thanks,

> .
> 

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