From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: John Snow <jsnow@redhat.com>, qemu-devel@nongnu.org
Cc: kwolf@redhat.com, pbonzini@redhat.com,
Vladimir Sementsov-Ogievskiy <vsementsov@parallels.com>,
stefanha@redhat.com, den@openvz.org
Subject: Re: [Qemu-devel] [PATCH 2/8] qcow2: add dirty-bitmaps feature
Date: Wed, 26 Aug 2015 17:14:26 +0300 [thread overview]
Message-ID: <55DDC9C2.2000706@virtuozzo.com> (raw)
In-Reply-To: <55DDBC06.2080101@virtuozzo.com>
On 26.08.2015 16:15, Vladimir Sementsov-Ogievskiy wrote:
> On 13.06.2015 00:55, John Snow wrote:
>>
>> On 06/08/2015 11:21 AM, Vladimir Sementsov-Ogievskiy wrote:
>>> From: Vladimir Sementsov-Ogievskiy <vsementsov@parallels.com>
>>>
>>> Adds dirty-bitmaps feature to qcow2 format as specified in
>>> docs/specs/qcow2.txt
>>>
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@parallels.com>
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>> ---
> ...
>>> +int qcow2_dirty_bitmap_store(BlockDriverState *bs, uint8_t *buf,
>>> + const char *name, uint64_t size,
>>> + int granularity)
>>> +{
>>> + BDRVQcowState *s = bs->opaque;
>>> + int cl_size = s->cluster_size;
>>> + int i, dirty_bitmap_index, ret = 0, n;
>>> + uint64_t *l1_table;
>>> + QCowDirtyBitmap *bm;
>>> + uint64_t buf_size;
>>> + uint8_t *p;
>>> + int sector_granularity = granularity >> BDRV_SECTOR_BITS;
>>> +
>>> + /* find/create dirty bitmap */
>>> + dirty_bitmap_index = find_dirty_bitmap_by_name(bs, name);
>>> + if (dirty_bitmap_index >= 0) {
>>> + bm = s->dirty_bitmaps + dirty_bitmap_index;
>>> +
>>> + if (size != bm->bitmap_size ||
>>> + granularity != bm->bitmap_granularity) {
>>> + qcow2_dirty_bitmap_delete(bs, name, NULL);
>> If this fails, we should 'return ret'.
>>
>>> + dirty_bitmap_index = -1;
>>> + }
>>> + }
>> Oh, find_dirty_bitmap_by_name only looks by name, but then you check to
>> make sure the size and granularity matches. If it doesn't, you actually
>> create a new bitmap with the *same name* but different attributes, and
>> delete the old one.
>>
>> Is that appropriate? I guess if we're already here in store, it means we
>> made it past the add checks... which means for whatever reason we
>> definitely want to store *this* bitmap...
>>
>> I think this code is a little extraneous, it might be best to just issue
>> an ultimatum that "You can't have two bitmaps with the same name in a
>> file." and let that be that -- finding something with the wrong size
>> would just simply be an error.
>>
>>> + if (dirty_bitmap_index < 0) {
>>> + qcow2_dirty_bitmap_create(bs, name, size, granularity);
>> If this fails, we need to return ret immediately.
>
> Not agree. I think it's ok for qcow2_dirty_bitmap_store to store given
> bitmap if it can. It can in two cases (in next patchset version):
>
> 1) found the bitmap with the same name, size and granularity: it is
> assumed to be the previous version and will be rewritten
> 2) not found the bitmap: it's ok, just save it.. This case works when
> the bitmap was created while qemu runs.
>
Oh, sorry. You mean,
ret = qcow2_dirty_bitmap_create ...
if (ret < 0) {
return ret;
}
, ok
>
>
>>
>>> + dirty_bitmap_index = s->nb_dirty_bitmaps - 1;
>>> + }
>>> + bm = s->dirty_bitmaps + dirty_bitmap_index;
>>> +
>>> + /* read l1 table */
>>> + l1_table = g_malloc(bm->l1_size * sizeof(uint64_t));
>>> + ret = bdrv_pread(bs->file, bm->l1_table_offset, l1_table,
>>> + bm->l1_size * sizeof(uint64_t));
>>> + if (ret < 0) {
>>> + goto finish;
>>> + }
>>> +
>>> + buf_size = (((size - 1) / sector_granularity) >> 3) + 1;
>>> + buf_size = align_offset(buf_size, 4);
>>> + n = buf_size / cl_size;
>>> + p = buf;
>>> + for (i = 0; i < bm->l1_size; ++i) {
>>> + uint64_t addr = be64_to_cpu(l1_table[i]) & ~511;
>>> + int write_size = (i == n ? (buf_size % cl_size) : cl_size);
>>> +
>>> + if (buffer_is_zero(p, write_size)) {
>>> + if (addr) {
>>> + qcow2_free_clusters(bs, addr, cl_size,
>>> + QCOW2_DISCARD_ALWAYS);
>>> + }
>>> + l1_table[i] = cpu_to_be64(1);
>>> + } else {
>>> + if (!addr) {
>>> + addr = qcow2_alloc_clusters(bs, cl_size);
>>> + l1_table[i] = cpu_to_be64(addr);
>>> + }
>>> +
>>> + ret = bdrv_pwrite(bs->file, addr, p, write_size);
>>> + if (ret < 0) {
>>> + goto finish;
>>> + }
>>> + }
>>> +
>>> + p += cl_size;
>>> + }
>>> +
>>> + ret = bdrv_pwrite(bs->file, bm->l1_table_offset, l1_table,
>>> + bm->l1_size * sizeof(uint64_t));
>>> + if (ret < 0) {
>>> + goto finish;
>>> + }
>>> +
>>> +finish:
>>> + g_free(l1_table);
>>> + return ret;
>>> +}
>>> +/* if no id is provided, a new one is constructed */
>>> +int qcow2_dirty_bitmap_create(BlockDriverState *bs, const char *name,
>
--
Best regards,
Vladimir
* now, @virtuozzo.com instead of @parallels.com. Sorry for this inconvenience.
next prev parent reply other threads:[~2015-08-26 14:14 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-08 15:21 [Qemu-devel] [PATCH v2 RFC 0/8] block: persistent dirty bitmaps Vladimir Sementsov-Ogievskiy
2015-06-08 15:21 ` [Qemu-devel] [PATCH 1/8] spec: add qcow2-dirty-bitmaps specification Vladimir Sementsov-Ogievskiy
2015-06-09 16:01 ` John Snow
2015-06-09 17:03 ` Stefan Hajnoczi
2015-06-10 8:19 ` Vladimir Sementsov-Ogievskiy
2015-06-10 8:49 ` Vladimir Sementsov-Ogievskiy
2015-06-10 13:00 ` Eric Blake
2015-06-11 10:16 ` Vladimir Sementsov-Ogievskiy
2015-06-10 13:24 ` Stefan Hajnoczi
2015-06-11 10:19 ` Vladimir Sementsov-Ogievskiy
2015-06-11 13:03 ` Stefan Hajnoczi
2015-06-11 16:21 ` John Snow
2015-06-12 10:28 ` Stefan Hajnoczi
2015-06-12 15:19 ` John Snow
2015-06-10 15:34 ` Kevin Wolf
2015-06-11 10:25 ` Vladimir Sementsov-Ogievskiy
2015-06-11 16:30 ` John Snow
2015-06-12 8:33 ` Kevin Wolf
2015-08-24 10:46 ` Vladimir Sementsov-Ogievskiy
2015-08-24 13:30 ` Vladimir Sementsov-Ogievskiy
2015-08-24 14:08 ` Vladimir Sementsov-Ogievskiy
2015-08-24 14:04 ` Vladimir Sementsov-Ogievskiy
2015-08-31 22:21 ` Eric Blake
2015-08-31 22:24 ` John Snow
2015-06-08 15:21 ` [Qemu-devel] [PATCH 2/8] qcow2: add dirty-bitmaps feature Vladimir Sementsov-Ogievskiy
2015-06-09 16:52 ` Stefan Hajnoczi
2015-06-10 14:30 ` Stefan Hajnoczi
2015-06-12 19:02 ` John Snow
2015-06-15 14:42 ` Stefan Hajnoczi
2015-06-23 17:57 ` John Snow
2015-06-24 9:39 ` Stefan Hajnoczi
2015-08-14 17:14 ` Vladimir Sementsov-Ogievskiy
2015-08-26 9:09 ` Stefan Hajnoczi
2015-06-11 23:04 ` John Snow
2015-06-15 14:05 ` Vladimir Sementsov-Ogievskiy
2015-06-15 16:53 ` John Snow
2015-06-12 21:55 ` John Snow
2015-08-26 13:15 ` Vladimir Sementsov-Ogievskiy
2015-08-26 14:14 ` Vladimir Sementsov-Ogievskiy [this message]
2015-08-27 12:43 ` Vladimir Sementsov-Ogievskiy
2015-06-08 15:21 ` [Qemu-devel] [PATCH 3/8] block: store persistent dirty bitmaps Vladimir Sementsov-Ogievskiy
2015-06-08 15:21 ` [Qemu-devel] [PATCH 4/8] block: add bdrv_load_dirty_bitmap Vladimir Sementsov-Ogievskiy
2015-06-09 16:01 ` Stefan Hajnoczi
2015-06-10 22:33 ` John Snow
2015-06-11 10:41 ` Vladimir Sementsov-Ogievskiy
2015-06-08 15:21 ` [Qemu-devel] [PATCH 5/8] qcow2: add qcow2_dirty_bitmap_delete_all Vladimir Sementsov-Ogievskiy
2015-06-08 15:21 ` [Qemu-devel] [PATCH 6/8] qcow2: add autoclear bit for dirty bitmaps Vladimir Sementsov-Ogievskiy
2015-06-09 15:49 ` Stefan Hajnoczi
2015-06-09 15:50 ` Stefan Hajnoczi
2015-08-27 7:45 ` Vladimir Sementsov-Ogievskiy
2015-08-31 11:06 ` Vladimir Sementsov-Ogievskiy
2015-08-31 22:39 ` Eric Blake
2015-08-31 22:50 ` Eric Blake
2015-06-10 23:42 ` John Snow
2015-06-11 8:35 ` Kevin Wolf
2015-06-11 10:49 ` Vladimir Sementsov-Ogievskiy
2015-06-11 16:36 ` John Snow
2015-06-08 15:21 ` [Qemu-devel] [PATCH 7/8] qemu: command line option " Vladimir Sementsov-Ogievskiy
2015-06-11 20:57 ` John Snow
2015-06-12 21:49 ` John Snow
2015-06-08 15:21 ` [Qemu-devel] [PATCH 8/8] iotests: test internal persistent dirty bitmap Vladimir Sementsov-Ogievskiy
2015-06-09 16:17 ` Eric Blake
2015-06-10 15:27 ` [Qemu-devel] [PATCH v2 RFC 0/8] block: persistent dirty bitmaps Stefan Hajnoczi
2015-06-11 11:22 ` Vladimir Sementsov-Ogievskiy
2015-06-11 13:14 ` Stefan Hajnoczi
2015-06-11 20:06 ` Stefan Hajnoczi
2015-06-12 9:58 ` Denis V. Lunev
2015-06-12 10:36 ` Stefan Hajnoczi
2015-08-26 6:26 ` Vladimir Sementsov-Ogievskiy
2015-08-26 9:13 ` Stefan Hajnoczi
2015-06-12 19:34 ` John Snow
2015-06-17 14:29 ` Vladimir Sementsov-Ogievskiy
2015-06-24 0:21 ` John Snow
2015-07-08 12:24 ` Vladimir Sementsov-Ogievskiy
2015-07-08 15:21 ` John Snow
2015-08-27 10:08 ` Vladimir Sementsov-Ogievskiy
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