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spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:53944 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hZNRB-0006Fc-Bl for qemu-devel@archiver.kernel.org; Fri, 07 Jun 2019 18:34:17 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51388) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hZN2W-0005nV-Mb for qemu-devel@nongnu.org; Fri, 07 Jun 2019 18:08:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hZN2Q-0003IV-Jh for qemu-devel@nongnu.org; Fri, 07 Jun 2019 18:08:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53262) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hZN28-0002sq-9E; Fri, 07 Jun 2019 18:08:24 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B9B1188319; Fri, 7 Jun 2019 22:08:20 +0000 (UTC) Received: from [10.10.120.179] (ovpn-120-179.rdu2.redhat.com [10.10.120.179]) by smtp.corp.redhat.com (Postfix) with ESMTP id E5B905D9CC; Fri, 7 Jun 2019 22:08:18 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" , "qemu-devel@nongnu.org" References: <20190606184159.979-1-jsnow@redhat.com> <20190606184159.979-3-jsnow@redhat.com> <70a53585-bdc6-1877-01f5-1b2d1aad8de6@virtuozzo.com> <5c62c56e-416c-e72e-e51f-8dcc1be96d53@virtuozzo.com> From: John Snow Openpgp: preference=signencrypt Autocrypt: addr=jsnow@redhat.com; prefer-encrypt=mutual; keydata= mQINBFTKefwBEAChvwqYC6saTzawbih87LqBYq0d5A8jXYXaiFMV/EvMSDqqY4EY6whXliNO IYzhgrPEe7ZmPxbCSe4iMykjhwMh5byIHDoPGDU+FsQty2KXuoxto+ZdrP9gymAgmyqdk3aV vzzmCa3cOppcqKvA0Kqr10UeX/z4OMVV390V+DVWUvzXpda45/Sxup57pk+hyY52wxxjIqef rj8u5BN93s5uCVTus0oiVA6W+iXYzTvVDStMFVqnTxSxlpZoH5RGKvmoWV3uutByQyBPHW2U 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rCDQYyakH2tJNQgkXkeLodBKF4bHiBbuwj0E39S9wmGgg+q4OTnAO/yhQGknle7a7G5xHBwE i0HjnLoJP5jDcoMTabZTIazXmJz3pKM11HYJ5/ZsTIf3ZRJJKIvXJpbmcAPVwTZII6XxiJdh RSSX4Mvd5pL/+5WI6NTdW6DMfigTtdd85fe6PwBNVJL2ZvBfsBJZ5rxg1TOH3KLsYBqBTgW2 glQofxhkJhDEcvjLhe3Y2BlbCWKOmvM8XS9TRt0OwUs= Message-ID: <1992aeff-b0fc-381b-7364-b600094f75bf@redhat.com> Date: Fri, 7 Jun 2019 18:08:17 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <5c62c56e-416c-e72e-e51f-8dcc1be96d53@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Fri, 07 Jun 2019 22:08:20 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 2/5] block/dirty-bitmap: Refactor bdrv_can_store_new_bitmap X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Kevin Wolf , Markus Armbruster , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/7/19 2:17 PM, Vladimir Sementsov-Ogievskiy wrote: > 07.06.2019 21:10, John Snow wrote: >> >> >> On 6/7/19 10:29 AM, Vladimir Sementsov-Ogievskiy wrote: >>> 06.06.2019 21:41, John Snow wrote: >>>> Instead of bdrv_can_store_new_bitmap, rework this as >>>> bdrv_add_persistent_dirty_bitmap. This makes a more obvious symmetry >>>> with bdrv_remove_persistent_dirty_bitmap. Most importantly, we are free >>>> to modify the driver state because we know we ARE adding a bitmap >>>> instead of simply being asked if we CAN store one. >>>> >>>> As part of this symmetry, move this function next to >>>> bdrv_remove_persistent_bitmap in block/dirty-bitmap.c. >>>> >>>> To cement this semantic distinction, use a bitmap object instead of the >>>> (name, granularity) pair as this allows us to set persistence as a >>>> condition of the "add" succeeding. >>>> >>>> Notably, the qcow2 implementation still does not actually store the new >>>> bitmap at add time, but merely ensures that it will be able to at store >>>> time. >>>> >>>> Signed-off-by: John Snow >>>> --- >>>> block/qcow2.h | 5 ++--- >>>> include/block/block.h | 2 -- >>>> include/block/block_int.h | 5 ++--- >>>> include/block/dirty-bitmap.h | 3 +++ >>>> block.c | 22 --------------------- >>>> block/dirty-bitmap.c | 38 ++++++++++++++++++++++++++++++++++++ >>>> block/qcow2-bitmap.c | 24 ++++++++++++++--------- >>>> block/qcow2.c | 2 +- >>>> blockdev.c | 19 +++++++----------- >>>> 9 files changed, 68 insertions(+), 52 deletions(-) >>>> >>>> diff --git a/block/qcow2.h b/block/qcow2.h >>>> index fc1b0d3c1e..95d723d3c0 100644 >>>> --- a/block/qcow2.h >>>> +++ b/block/qcow2.h >>>> @@ -742,9 +742,8 @@ int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp); >>>> int qcow2_truncate_bitmaps_check(BlockDriverState *bs, Error **errp); >>>> void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp); >>>> int qcow2_reopen_bitmaps_ro(BlockDriverState *bs, Error **errp); >>>> -bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs, >>>> - const char *name, >>>> - uint32_t granularity, >>>> +int qcow2_add_persistent_dirty_bitmap(BlockDriverState *bs, >>>> + BdrvDirtyBitmap *bitmap, >>>> Error **errp); >>>> void qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs, >>>> const char *name, >>>> diff --git a/include/block/block.h b/include/block/block.h >>>> index f9415ed740..6d520f3b59 100644 >>>> --- a/include/block/block.h >>>> +++ b/include/block/block.h >>>> @@ -683,8 +683,6 @@ void bdrv_add_child(BlockDriverState *parent, BlockDriverState *child, >>>> Error **errp); >>>> void bdrv_del_child(BlockDriverState *parent, BdrvChild *child, Error **errp); >>>> >>>> -bool bdrv_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name, >>>> - uint32_t granularity, Error **errp); >>>> /** >>>> * >>>> * bdrv_register_buf/bdrv_unregister_buf: >>>> diff --git a/include/block/block_int.h b/include/block/block_int.h >>>> index 06df2bda1b..93bbb66cd0 100644 >>>> --- a/include/block/block_int.h >>>> +++ b/include/block/block_int.h >>>> @@ -537,9 +537,8 @@ struct BlockDriver { >>>> * field of BlockDirtyBitmap's in case of success. >>>> */ >>>> int (*bdrv_reopen_bitmaps_rw)(BlockDriverState *bs, Error **errp); >>>> - bool (*bdrv_can_store_new_dirty_bitmap)(BlockDriverState *bs, >>>> - const char *name, >>>> - uint32_t granularity, >>>> + int (*bdrv_add_persistent_dirty_bitmap)(BlockDriverState *bs, >>>> + BdrvDirtyBitmap *bitmap, >>>> Error **errp); >>>> void (*bdrv_remove_persistent_dirty_bitmap)(BlockDriverState *bs, >>>> const char *name, >>>> diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h >>>> index 8044ace63e..c37edbe05f 100644 >>>> --- a/include/block/dirty-bitmap.h >>>> +++ b/include/block/dirty-bitmap.h >>>> @@ -38,6 +38,9 @@ int bdrv_dirty_bitmap_check(const BdrvDirtyBitmap *bitmap, uint32_t flags, >>>> Error **errp); >>>> void bdrv_release_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap); >>>> void bdrv_release_named_dirty_bitmaps(BlockDriverState *bs); >>>> +int bdrv_add_persistent_dirty_bitmap(BlockDriverState *bs, >>>> + BdrvDirtyBitmap *bitmap, >>>> + Error **errp); >>>> void bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs, >>>> const char *name, >>>> Error **errp); >>>> diff --git a/block.c b/block.c >>>> index e3e77feee0..6aec36b7c9 100644 >>>> --- a/block.c >>>> +++ b/block.c >>>> @@ -6379,25 +6379,3 @@ void bdrv_del_child(BlockDriverState *parent_bs, BdrvChild *child, Error **errp) >>>> >>>> parent_bs->drv->bdrv_del_child(parent_bs, child, errp); >>>> } >>>> - >>>> -bool bdrv_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name, >>>> - uint32_t granularity, Error **errp) >>>> -{ >>>> - BlockDriver *drv = bs->drv; >>>> - >>>> - if (!drv) { >>>> - error_setg_errno(errp, ENOMEDIUM, >>>> - "Can't store persistent bitmaps to %s", >>>> - bdrv_get_device_or_node_name(bs)); >>>> - return false; >>>> - } >>>> - >>>> - if (!drv->bdrv_can_store_new_dirty_bitmap) { >>>> - error_setg_errno(errp, ENOTSUP, >>>> - "Can't store persistent bitmaps to %s", >>>> - bdrv_get_device_or_node_name(bs)); >>>> - return false; >>>> - } >>>> - >>>> - return drv->bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp); >>>> -} >>>> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c >>>> index 49646a30e6..615f8480b2 100644 >>>> --- a/block/dirty-bitmap.c >>>> +++ b/block/dirty-bitmap.c >>>> @@ -466,6 +466,44 @@ void bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs, >>>> } >>>> } >>>> >>>> +int bdrv_add_persistent_dirty_bitmap(BlockDriverState *bs, >>>> + BdrvDirtyBitmap *bitmap, >>>> + Error **errp) >>> >>> strange thing for me: "bitmap" in function name is _not_ the same >>> thing as @bitmap argument.. as if it the same, >>> function adds "persistent bitmap", but @bitmap is not persistent yet, >>> so may be function, don't add persistent bitmap, but marks bitmap persistent? >>> >>> >>> Ok, I can think of it like "add persistent dirty bitmap to driver. if succeed, set >>> bitmap.persistent flag" >>> >> >> Yeah, I meant "Add bitmap to file", where the persistence is implied >> because it's part of the file. The bitmap is indeed not YET persistent, >> but becomes so as a condition of this call succeeding. >> >> Do you have a suggestion for a better name? I liked the symmetry with >> 'remove' so that there was an obvious "add bitmap" and "remove bitmap". >> >> Of course, when you remove, it is indeed persistent, so >> "remove_persistent_dirty_bitmap" makes sense there. >> >>> >>>> +{ >>>> + BlockDriver *drv = bs->drv; >>>> + int ret; >>>> + >>>> + if (bdrv_dirty_bitmap_get_persistence(bitmap)) { >>>> + error_setg(errp, "Bitmap '%s' is already persistent, " >>>> + "and cannot be re-added to node '%s'", >>>> + bdrv_dirty_bitmap_name(bitmap), >>>> + bdrv_get_device_or_node_name(bs)); >>>> + return -EINVAL; >>>> + } >>>> + >>>> + if (!drv) { >>>> + error_setg_errno(errp, ENOMEDIUM, >>>> + "Can't store persistent bitmaps to %s", >>>> + bdrv_get_device_or_node_name(bs)); >>>> + return -ENOMEDIUM; >>>> + } >>>> + >>>> + if (!drv->bdrv_add_persistent_dirty_bitmap) { >>>> + error_setg_errno(errp, ENOTSUP, >>>> + "Can't store persistent bitmaps to %s", >>>> + bdrv_get_device_or_node_name(bs)); >>>> + return -ENOTSUP; >>>> + } >>>> + >>>> + ret = drv->bdrv_add_persistent_dirty_bitmap(bs, bitmap, errp); >>>> + if (ret == 0) { >>>> + bdrv_dirty_bitmap_set_persistence(bitmap, true); >>>> + } >>>> + >>>> + return ret; >>>> +} >>>> + >>>> + >>>> void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap) >>>> { >>>> bdrv_dirty_bitmap_lock(bitmap); >>>> diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c >>>> index 83aee1a42a..c3a72ca782 100644 >>>> --- a/block/qcow2-bitmap.c >>>> +++ b/block/qcow2-bitmap.c >>>> @@ -1607,14 +1607,16 @@ int qcow2_reopen_bitmaps_ro(BlockDriverState *bs, Error **errp) >>>> return 0; >>>> } >>>> >>>> -bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs, >>>> - const char *name, >>>> - uint32_t granularity, >>>> +int qcow2_add_persistent_dirty_bitmap(BlockDriverState *bs, >>>> + BdrvDirtyBitmap *bitmap, >>>> Error **errp) >>>> { >>>> BDRVQcow2State *s = bs->opaque; >>>> bool found; >>>> Qcow2BitmapList *bm_list; >>>> + const char *name = bdrv_dirty_bitmap_name(bitmap); >>>> + uint32_t granularity = bdrv_dirty_bitmap_granularity(bitmap); >>>> + int ret = 0; >>> >>> dead assignment >>> >> >> Will take care of. >> >>>> >>>> if (s->qcow_version < 3) { >>>> /* Without autoclear_features, we would always have to assume >>>> @@ -1623,20 +1625,23 @@ bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs, >>>> * have to drop all dirty bitmaps (defeating their purpose). >>>> */ >>>> error_setg(errp, "Cannot store dirty bitmaps in qcow2 v2 files"); >>>> + ret = -ENOTSUP; >>>> goto fail; >>>> } >>>> >>>> - if (check_constraints_on_bitmap(bs, name, granularity, errp) != 0) { >>>> + ret = check_constraints_on_bitmap(bs, name, granularity, errp); >>>> + if (ret) { >>> >>> hmm, in other places you prefere >>> if ((ret = ...)) { >>> syntax >>> >> >> I have to get rid of those anyway, they violate our coding style. I'll >> be replacing them all with this full style. >> >>>> goto fail; >>>> } >>>> >>>> if (s->nb_bitmaps == 0) { >>>> - return true; >>>> + return 0; >>>> } >>>> >>>> if (s->nb_bitmaps >= QCOW2_MAX_BITMAPS) { >>>> error_setg(errp, >>>> "Maximum number of persistent bitmaps is already reached"); >>>> + ret = -EOVERFLOW; >>>> goto fail; >>>> } >>>> >>>> @@ -1644,24 +1649,25 @@ bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs, >>>> QCOW2_MAX_BITMAP_DIRECTORY_SIZE) >>>> { >>>> error_setg(errp, "Not enough space in the bitmap directory"); >>>> + ret = -EOVERFLOW; >>>> goto fail; >>>> } >>>> >>>> - if (bitmap_list_load(bs, &bm_list, errp)) { >>>> + if ((ret = bitmap_list_load(bs, &bm_list, errp))) { >>> >>> interesting, now we load all bitmaps, so, may be, we don't need to load list every time, >>> but may use bs.dirty_bitmaps to check such things.. But it seems unsafe >>> >> >> Yeah, I would like to cache this list eventually, but I ran into a lot >> of hassle with it last time I tried and put it off for now. >> >> I think we should definitely be able to. >> >> And in fact, if we did, we could even add these bitmaps to the bm_list >> as soon as _add_ is called and drop the need for the queued counters. > > Personally I like the old _can_add_ :) > > But you want to make this function really do something with driver, so "_can_" is not good > ofcourse and _add_ is better. And any kind of _mark_persistent_ or _make_persistent_ will > be in a bad relation with simple setter _set_persistence() which we already have and which > doesn't imply any complicated logic.. > I think it's a simpler design to have "add" and "remove" callbacks and be more direct about it. Of course, the qcow2 implementation is free to avoid a write to disk on add if it wishes, but I don't like the idea of having to call "can_store" and then later a "do_store" or any such thing. You could say that can_store is the check and then mark persistent is the actual action, but then why keep them separate? I like the link between calling the driver and the later store to be obvious. I feel like marking the bitmap persistent without the knowledge or consent of the driver is bound to cause trouble sooner or later, so I'd rather make the persistent call a condition of the store check succeeding. > On the other hand I still not sure that we need track "queued" bitmaps in qcow2 driver, as we > can calculate their number and needed size of directory in any moment, not extending the qcow2 > state.. > Do we want to add an O(N) check because we don't want to spend 12 bytes? --js