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Date:   Tue, 28 Sep 2021 12:08:14 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] f2fs: skip f2fs_preallocate_blocks() for overwrite case
Message-ID: <YVNoHudG5c65X85G@google.com>
References: <20210928151911.11189-1-chao@kernel.org>
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In-Reply-To: <20210928151911.11189-1-chao@kernel.org>
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On 09/28, Chao Yu wrote:
> In f2fs_file_write_iter(), let's use f2fs_overwrite_io() to
> check whethere it is overwrite case, for such case, we can skip
> f2fs_preallocate_blocks() in order to avoid f2fs_do_map_lock(),
> which may be blocked by checkpoint() potentially.
> 
> Signed-off-by: Chao Yu <chao@kernel.org>
> ---
>  fs/f2fs/file.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 13deae03df06..51fecb2f4db5 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -4321,6 +4321,10 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  		preallocated = true;
>  		target_size = iocb->ki_pos + iov_iter_count(from);
>  
> +		if (f2fs_overwrite_io(inode, iocb->ki_pos,
> +						iov_iter_count(from)))
> +			goto write;

This calls f2fs_map_blocks() which can be duplicate, if it's not the overwirte
case. Do we have other benefit?

> +
>  		err = f2fs_preallocate_blocks(iocb, from);
>  		if (err) {
>  out_err:
> -- 
> 2.32.0