Re: [f2fs-dev] [PATCH 2/2] f2fs: Return EOF on unaligned end of file DIO read

[Jaegeuk Kim <jaegeuk@kernel.org>]

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


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