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dkim=none (message not signed) header.d=none;nongnu.org; dmarc=none action=none header.from=virtuozzo.com; Received: from VI1PR08MB5503.eurprd08.prod.outlook.com (2603:10a6:803:137::19) by VI1PR0801MB1854.eurprd08.prod.outlook.com (2603:10a6:800:5c::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4242.21; Sat, 19 Jun 2021 11:12:15 +0000 Received: from VI1PR08MB5503.eurprd08.prod.outlook.com ([fe80::5d2:a831:a04c:66fb]) by VI1PR08MB5503.eurprd08.prod.outlook.com ([fe80::5d2:a831:a04c:66fb%4]) with mapi id 15.20.4242.023; Sat, 19 Jun 2021 11:12:15 +0000 Subject: Re: [PATCH 5/6] block/nbd: Do not force-cap *pnum To: Eric Blake , Max Reitz Cc: qemu-block@nongnu.org, Kevin Wolf , qemu-devel@nongnu.org References: <20210617155247.442150-1-mreitz@redhat.com> <20210617155247.442150-6-mreitz@redhat.com> <20210618202020.3t777osf6doytjal@redhat.com> From: Vladimir Sementsov-Ogievskiy Message-ID: <656b17d3-0cc1-e1da-431d-133ab5502eb1@virtuozzo.com> Date: Sat, 19 Jun 2021 14:12:12 +0300 User-Agent: Mozilla/5.0 (X11; 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envelope-from=vsementsov@virtuozzo.com; helo=EUR03-VE1-obe.outbound.protection.outlook.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, MSGID_FROM_MTA_HEADER=0.001, NICE_REPLY_A=-0.202, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 18.06.2021 23:20, Eric Blake wrote: > On Thu, Jun 17, 2021 at 05:52:46PM +0200, Max Reitz wrote: >> bdrv_co_block_status() does it for us, we do not need to do it here. >> >> The advantage of not capping *pnum is that bdrv_co_block_status() can >> cache larger data regions than requested by its caller. >> >> Signed-off-by: Max Reitz >> --- >> block/nbd.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) > > Reviewed-by: Eric Blake > >> >> diff --git a/block/nbd.c b/block/nbd.c >> index 616f9ae6c4..930bd234de 100644 >> --- a/block/nbd.c >> +++ b/block/nbd.c >> @@ -1702,7 +1702,7 @@ static int coroutine_fn nbd_client_co_block_status( >> .type = NBD_CMD_BLOCK_STATUS, >> .from = offset, >> .len = MIN(QEMU_ALIGN_DOWN(INT_MAX, bs->bl.request_alignment), >> - MIN(bytes, s->info.size - offset)), >> + s->info.size - offset), >> .flags = NBD_CMD_FLAG_REQ_ONE, > > I'd love to someday get rid of using NBD_CMD_FLAG_REQ_ONE (so the > server can reply with more extents in one go), but that's a bigger > task and unrelated to your block-layer cache. > I think for this to work, the generic block_status should be updated so we can work with several extents in one go. -- Best regards, Vladimir