Re: [Qemu-devel] [PATCH 01/17] vvfat: Use BdrvChild for s->qcow

[Max Reitz]

On 21.06.2016 11:21, Kevin Wolf wrote:
> vvfat uses a temporary qcow file to cache written data in read-write
> mode. In order to do things properly, this should show up in the BDS
> graph and I/O should go through BdrvChild like for every other node.
> 
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>  block/vvfat.c | 66 
> ++++++++++++++++++++++++++++++++++++++---------------------
>  1 file changed, 43 insertions(+), 23 deletions(-)

checkpatch.pl has some complaints:

ERROR: "foo* bar" should be "foo *bar"
#43: FILE: block/vvfat.c:348:
+    BdrvChild* qcow;

ERROR: spaces required around that '-' (ctx:VxV)
#81: FILE: block/vvfat.c:1392:
+            if (bdrv_is_allocated(s->qcow->bs, sector_num,
nb_sectors-i, &n)) {
                                                                      ^

ERROR: spaces required around that '*' (ctx:VxV)
#84: FILE: block/vvfat.c:1395:
+                if (bdrv_read(s->qcow->bs, sector_num, buf + i*0x200, n)) {
                                                               ^

ERROR: code indent should never use tabs
#103: FILE: block/vvfat.c:1677:
+^I                                     cluster2sector(s, cluster_num) + i,$

The fourth is actually something you introduced (more or less, at least
all of the surrounding code uses spaces), so that must be fixed.

The rest is preexisting, but I think some of those are worth fixing
still; namely all but the first. You know how I think about the first
and I know how you think about it, so I won't complain if it's
surrounded by code in the same style.

> diff --git a/block/vvfat.c b/block/vvfat.c
> index 6d2e21c..2eb2536 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c

[...]

> @@ -2949,7 +2958,7 @@ write_target_commit(BlockDriverState *bs, uint64_t 
> offset, uint64_t bytes,
>  
>  static void write_target_close(BlockDriverState *bs) {
>      BDRVVVFATState* s = *((BDRVVVFATState**) bs->opaque);
> -    bdrv_unref(s->qcow);
> +    bdrv_unref_child(NULL, s->qcow);

Not that it matters, but why not s->bs instead of NULL?

>      g_free(s->qcow_filename);
>  }
>  
> @@ -2959,8 +2968,19 @@ static BlockDriver vvfat_write_target = {
>      .bdrv_close         = write_target_close,
>  };
>  
> -static int enable_write_target(BDRVVVFATState *s, Error **errp)
> +static void vvfat_qcow_options(int *child_flags, QDict *child_options,
> +                               int parent_flags, QDict *parent_options)
>  {
> +    *child_flags = BDRV_O_RDWR | BDRV_O_NO_FLUSH;
> +}
> +
> +const BdrvChildRole child_vvfat_qcow = {

Any reason for not making this static?

> +    .inherit_options    = vvfat_qcow_options,
> +};
> +
> +static int enable_write_target(BlockDriverState *bs, Error **errp)
> +{
> +    BDRVVVFATState *s = bs->opaque;
>      BlockDriver *bdrv_qcow = NULL;
>      BlockDriverState *backing;
>      QemuOpts *opts = NULL;
> @@ -2999,8 +3019,8 @@ static int enable_write_target(BDRVVVFATState *s, Error 
> **errp)
>  
>      options = qdict_new();
>      qdict_put(options, "driver", qstring_from_str("qcow"));
> -    s->qcow = bdrv_open(s->qcow_filename, NULL, options,
> -                        BDRV_O_RDWR | BDRV_O_NO_FLUSH, errp);
> +    s->qcow = bdrv_open_child(s->qcow_filename, options, "qcow", bs,

I'd have called it "write_target", but, well.

Max

> +                              &child_vvfat_qcow, false, errp);
>      if (!s->qcow) {
>          ret = -EINVAL;
>          goto err;
>

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