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From: Jaegeuk Kim <jaegeuk@kernel.org>
To: Gabriel Krisman Bertazi <krisman@collabora.com>
Cc: viro@zeniv.linux.org.uk, chao@kernel.org,
	linux-fsdevel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net, kernel@collabora.com
Subject: Re: [PATCH 2/2] f2fs: Return EOF on unaligned end of file DIO read
Date: Thu, 20 Aug 2020 09:13:59 -0700	[thread overview]
Message-ID: <20200820161359.GB2375181@google.com> (raw)
In-Reply-To: <20200819200731.2972195-3-krisman@collabora.com>

Hi Gabriel,

Thank you for the patch. Let me take this separately from the patch set.

Thanks,

On 08/19, Gabriel Krisman Bertazi wrote:
> Reading past end of file returns EOF for aligned reads but -EINVAL for
> unaligned reads on f2fs.  While documentation is not strict about this
> corner case, most filesystem returns EOF on this case, like iomap
> filesystems.  This patch consolidates the behavior for f2fs, by making
> it return EOF(0).
> 
> it can be verified by a read loop on a file that does a partial read
> before EOF (A file that doesn't end at an aligned address).  The
> following code fails on an unaligned file on f2fs, but not on
> btrfs, ext4, and xfs.
> 
>   while (done < total) {
>     ssize_t delta = pread(fd, buf + done, total - done, off + done);
>     if (!delta)
>       break;
>     ...
>   }
> 
> It is arguable whether filesystems should actually return EOF or
> -EINVAL, but since iomap filesystems support it, and so does the
> original DIO code, it seems reasonable to consolidate on that.
> 
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
> ---
>  fs/f2fs/data.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 5f527073143e..d9834ffe1da9 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3510,6 +3510,9 @@ static int check_direct_IO(struct inode *inode, struct iov_iter *iter,
>  	unsigned long align = offset | iov_iter_alignment(iter);
>  	struct block_device *bdev = inode->i_sb->s_bdev;
>  
> +	if (iov_iter_rw(iter) == READ && offset >= i_size_read(inode))
> +		return 1;
> +
>  	if (align & blocksize_mask) {
>  		if (bdev)
>  			blkbits = blksize_bits(bdev_logical_block_size(bdev));
> -- 
> 2.28.0

  reply	other threads:[~2020-08-20 16:14 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-19 20:07 [PATCH 0/2] Consolidate DIO behavior on unaligned EOF read Gabriel Krisman Bertazi
2020-08-19 20:07 ` [PATCH 1/2] direct-io: defer alignment check until after EOF check Gabriel Krisman Bertazi
2020-08-26 14:28   ` Jan Kara
2020-08-19 20:07 ` [PATCH 2/2] f2fs: Return EOF on unaligned end of file DIO read Gabriel Krisman Bertazi
2020-08-20 16:13   ` Jaegeuk Kim [this message]
2020-08-21  1:37   ` Chao Yu

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