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Subject: Re: [f2fs-dev] [PATCH v3] f2fs: fix race of pending_pages in
 decompression
To:     Daeho Jeong <daeho43@gmail.com>
CC:     <linux-kernel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>,
        <kernel-team@android.com>, Jaegeuk Kim <jaegeuk@kernel.org>,
        Daeho Jeong <daehojeong@google.com>
References: <20201205042626.1113600-1-daeho43@gmail.com>
 <c3c41d53-2a99-17a2-223a-3d674613a417@huawei.com>
 <CACOAw_zwbmYHbUVUmzGMci9SaSVSrP8NXXavHBSSLxbAEOrMcw@mail.gmail.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <c45d327f-b669-a0ec-bd77-0c95dfd8db2c@huawei.com>
Date:   Mon, 7 Dec 2020 15:41:38 +0800
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On 2020/12/7 15:28, Daeho Jeong wrote:
>> It looks like it will be better to move this into merge condition?
>>
>>                  if (bio && (!page_is_mergeable(sbi, bio,
>>                                          *last_block_in_bio, blkaddr) ||
>>                      !f2fs_crypt_mergeable_bio(bio, inode, page->index, NULL) ||
>>                          f2fs_verify_mergeable_bio())) {
>>
> 
> I tried this for the first time, but it requires unnecessary checks
> within the compression cluster.

We only need to check f2fs_verify_mergeable_bio for i == 0 case? something like:

static bool f2fs_verify_mergeable_bio(struct bio *bio, bool verify, bool first_page)
{
	if (!first_page)
		return false;
	if (!verify)
		return false;

	ctx = bio->bi_private;
	if (!(ctx->enabled_steps & (1 << STEP_VERITY)))
		return true;
}

Thoughts?

> I wanted to just check one time in the beginning of the cluster.
> What do you think?

It's trivial, but I'm think about the readability... at least, one line comment
is needed to describe why we submit previous bio. :)

Thanks,

> .
>