linux-ext4 - Re: [PATCH] mke2fs: fix coping of empty file using fiemap

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Date:   Mon, 16 Jan 2017 17:37:08 -0800
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Artem Blagodarenko <artem.blagodarenko@...gate.com>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH] mke2fs: fix coping of empty file using fiemap

On Mon, Jan 16, 2017 at 07:59:17PM +0300, Artem Blagodarenko wrote:
> During filesystem creation with -d option files copied from given
> directory. If supported, FS_IOC_FIEMAP ioctl is used to get file
> extents. For empty file fm_mapped_extents is 0 and no error code
> is returned, because this is not fail situation.
> 
> Without this patch errno from previous operation is returned and
> successful FS_IOC_FIEMAP ioctl call for empty file is interpreted
> as error.
> 
> Signed-off-by: Artem Blagodarenko <artem.blagodarenko@...gate.com>
> ---
>  misc/create_inode.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/misc/create_inode.c b/misc/create_inode.c
> index 5122e56..6083d94 100644
> --- a/misc/create_inode.c
> +++ b/misc/create_inode.c
> @@ -510,7 +510,7 @@ static errcode_t try_fiemap_copy(ext2_filsys fs,
> int fd, ext2_file_t e2_file,
>          if (err < 0 && (errno == EOPNOTSUPP || errno == ENOTTY)) {
>              err = EXT2_ET_UNIMPLEMENTED;
>              goto out;
> -        } else if (err < 0 || fiemap_buf->fm_mapped_extents == 0) {
> +        } else if (err < 0 && fiemap_buf->fm_mapped_extents == 0) {

I think we want the loop to terminate any time fm_mapped_extents == 0,
not just in the case that err < 0 and fiemap_buf still reflects the
earlier memset(0)...

} else if (err < 0) {
	err = errno;
	goto out;
} else if (!fiemap_buf->fm_mapped_extents)
	goto out;

...right?

--D

>              err = errno;
>              goto out;
>          }
> --
> --
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