linux-ext4 - Re: [PATCH 10/31] libext2fs: Allow callers to punch a single block

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Date:	Tue, 1 Oct 2013 15:09:44 -0400
From:	jon ernst <jonernst07@...il.com>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
Cc:	"Theodore Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 10/31] libext2fs: Allow callers to punch a single block

On Mon, Sep 30, 2013 at 9:27 PM, Darrick J. Wong
<darrick.wong@...cle.com> wrote:
> The range of blocks to punch is treated as an inclusive range on both ends,
> i.e. if start=1 and end=2, both blocks 1 and 2 are punched out.  Thus, start ==
> end means that the caller wishes to punch a single block.  Remove the check
> that prevents us from punching a single block.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> ---
>  lib/ext2fs/ext2fs.h |    4 ++++
>  lib/ext2fs/punch.c  |    5 +----
>  2 files changed, 5 insertions(+), 4 deletions(-)
>
>
> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> index 311ceda..c37e00b 100644
> --- a/lib/ext2fs/ext2fs.h
> +++ b/lib/ext2fs/ext2fs.h
> @@ -1385,6 +1385,10 @@ extern errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
>                                           char *mtpt, int mtlen);
>
>  /* punch.c */
> +/*
> + * NOTE: This function removes from an inode the blocks "start", "end", and
> + * every block in between.
> + */
>  extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
>                               struct ext2_inode *inode,
>                               char *block_buf, blk64_t start,
> diff --git a/lib/ext2fs/punch.c b/lib/ext2fs/punch.c
> index 11c7668..aac1942 100644
> --- a/lib/ext2fs/punch.c
> +++ b/lib/ext2fs/punch.c
> @@ -315,9 +315,6 @@ extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
>         if (start > end)
>                 return EINVAL;
>
> -       if (start == end)
> -               return 0;
> -
>         /* Read inode structure if necessary */
>         if (!inode) {
>                 retval = ext2fs_read_inode(fs, ino, &inode_buf);
> @@ -332,7 +329,7 @@ extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
>
>                 if (start > ~0U)
>                         return 0;
> -               count = ((end - start) < ~0U) ? (end - start) : ~0U;
> +               count = ((end - start + 1) < ~0U) ? (end - start + 1) : ~0U;
can you simply put "count =  end - start + 1;" since you have checked
start > end case earlier.
>                 retval = ext2fs_punch_ind(fs, inode, block_buf,
>                                           (blk_t) start, count);
>         }
>
> --
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