Re: [PATCH v7 1/4] block: introducing 'bdrv_co_delete_file' interface

[Kevin Wolf <kwolf@redhat.com>]

Am 03.09.2019 um 15:57 hat Daniel Henrique Barboza geschrieben:
> Adding to Block Drivers the capability of being able to clean up
> its created files can be useful in certain situations. For the
> LUKS driver, for instance, a failure in one of its authentication
> steps can leave files in the host that weren't there before.
> 
> This patch adds the 'bdrv_co_delete_file' interface to block
> drivers and add it to the 'file' driver in file-posix.c.The

Missing space between "file-posix.c.The"

> implementation is given by 'raw_co_delete_file'.
> 
> Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>  block/file-posix.c        | 28 ++++++++++++++++++++++++++++
>  include/block/block_int.h |  6 ++++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/block/file-posix.c b/block/file-posix.c
> index fbeb0068db..52756de522 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -2390,6 +2390,33 @@ static int coroutine_fn raw_co_create_opts(const char *filename, QemuOpts *opts,
>      return raw_co_create(&options, errp);
>  }
>  
> +/**
> + * Co-routine function that erases a regular file.
> + */

We don't have function comments for other BdrvDriver callbacks. It may
be appropriate to have a comment when there is something special going
on here that differs from a normal implementation. But this specific
comment is even redundant with the function name, so I think we don't
need it.

> +static int coroutine_fn raw_co_delete_file(BlockDriverState *bs,
> +                                           Error **errp)
> +{
> +    struct stat st;
> +    int ret;
> +
> +    if (!(stat(bs->filename, &st) == 0) || !S_ISREG(st.st_mode)) {
> +        ret = -ENOENT;
> +        error_setg_errno(errp, -ret, "%s is not a regular file",
> +                         bs->filename);
> +        goto done;

There is no cleanup code, so a direct return -ENOENT would be simpler.

> +    }
> +
> +    ret = unlink(bs->filename);
> +    if (ret < 0) {
> +        ret = -errno;
> +        error_setg_errno(errp, -ret, "Error when deleting file %s",
> +                         bs->filename);
> +    }
> +
> +done:
> +    return ret;
> +}
> +
>  /*
>   * Find allocation range in @bs around offset @start.
>   * May change underlying file descriptor's file offset.
> @@ -2942,6 +2969,7 @@ BlockDriver bdrv_file = {
>      .bdrv_co_block_status = raw_co_block_status,
>      .bdrv_co_invalidate_cache = raw_co_invalidate_cache,
>      .bdrv_co_pwrite_zeroes = raw_co_pwrite_zeroes,
> +    .bdrv_co_delete_file = raw_co_delete_file,
>  
>      .bdrv_co_preadv         = raw_co_preadv,
>      .bdrv_co_pwritev        = raw_co_pwritev,
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index 0422acdf1c..a959ec2d1e 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -314,6 +314,12 @@ struct BlockDriver {
>       */
>      int coroutine_fn (*bdrv_co_flush)(BlockDriverState *bs);
>  
> +    /*
> +     * Delete a local created file.
> +     */

No reason to restrict this to "local", even if for now file-posix is the
only driver that implements it. This can change later.

The comment fits in a single line.

> +    int coroutine_fn (*bdrv_co_delete_file)(BlockDriverState *bs,
> +                                            Error **errp);
> +

Kevin