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Date: Thu, 18 Apr 2013 10:54:12 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130418085412.GB19587@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH V18 4/6] rename qcow2-cache.c to
 block-cache.c
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To: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
Cc: kwol@redhat.com, wdongxu@cn.ibm.com, qemu-devel@nongnu.org, stefanha@redhat.com

On Wed, Apr 10, 2013 at 04:11:51PM +0800, Dong Xu Wang wrote:

This patch does two things:
1. Rename and move qcow2-cache to block-cache.
2. Add a type enum to parameterize BLKDEBUG_EVENT() for L2, refcount,
   and bitmaps.

It's hard to review #2 since all lines are changed in the diff by #1.
In the future, please split patches that move code into two.

The first patch should simply move and rename - it should not include
code changes.

The second patch should contain code changes (i.e. adding the cache type
enum and parameterizing BLKDEBUG_EVENT()).

BTW, when splitting the patch into two for easy reviewing it also
becomes questionable whether to reassign authorship since 90+% of the
code is unchanged and simply moved.

> +    if (c->table_type == BLOCK_TABLE_REF) {
> +        BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_UPDATE_PART);
> +    } else if (c->table_type == BLOCK_TABLE_L2) {
> +        BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE);
> +    } else if (c->table_type == BLOCK_TABLE_BITMAP) {
> +        BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE);

BLKDBG_COW_WRITE is for writing out sectors from the backing file.  It
is not for updating the allocation bitmap.

Please pick an appropriate constant or define your own if none exists.

> +    if (read_from_disk) {
> +        if (c->table_type == BLOCK_TABLE_L2) {
> +            BLKDBG_EVENT(bs->file, BLKDBG_L2_LOAD);
> +        } else if (c->table_type == BLOCK_TABLE_BITMAP) {
> +            BLKDBG_EVENT(bs->file, BLKDBG_COW_READ);

Same here.