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Date:   Tue, 26 Nov 2019 08:33:15 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Damien Le Moal <damien.lemoal@wdc.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, Jaegeuk Kim <jaegeuk@kernel.org>,
        Chao Yu <yuchao0@huawei.com>, linux-fsdevel@vger.kernel.org,
        Javier Gonzalez <javier@javigon.com>,
        Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Subject: Re: [PATCH] f2fs: Fix direct IO handling
Message-ID: <20191126163315.GB3794@infradead.org>
References: <20191126075719.1046485-1-damien.lemoal@wdc.com>
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On Tue, Nov 26, 2019 at 04:57:19PM +0900, Damien Le Moal wrote:
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 5755e897a5f0..8ac2d3b70022 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1073,6 +1073,8 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>  	int flag;
>  	int err = 0;
>  	bool direct_io = iocb->ki_flags & IOCB_DIRECT;
> +	bool do_direct_io = direct_io &&
> +		!f2fs_force_buffered_io(inode, iocb, from);

I don't think this is the right fix.  The proper fix is to clear
IOCB_DIRECT when falling back to buffered I/O, preferably in the
filemap.c helpers as well.