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dkim=none (message not signed) header.d=none;redhat.com; dmarc=none action=none header.from=virtuozzo.com; Received: from AM7PR08MB5494.eurprd08.prod.outlook.com (2603:10a6:20b:dc::15) by AM5PR0801MB1906.eurprd08.prod.outlook.com (2603:10a6:203:48::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4523.15; Thu, 23 Sep 2021 21:50:44 +0000 Received: from AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::2817:53b3:f8b4:fe22]) by AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::2817:53b3:f8b4:fe22%9]) with mapi id 15.20.4544.015; Thu, 23 Sep 2021 21:50:44 +0000 Subject: Re: [PATCH v6 07/11] block: use int64_t instead of int in driver write_zeroes handlers To: Eric Blake Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, integration@gluster.org, kraxel@redhat.com, idryomov@gmail.com, berto@igalia.com, philmd@redhat.com, pl@kamp.de, ronniesahlberg@gmail.com, fam@euphon.net, sw@weilnetz.de, jsnow@redhat.com, stefanha@redhat.com, pbonzini@redhat.com, pavel.dovgaluk@ispras.ru, ari@tuxera.com, hreitz@redhat.com, kwolf@redhat.com References: <20210903102807.27127-1-vsementsov@virtuozzo.com> <20210903102807.27127-8-vsementsov@virtuozzo.com> <20210923203345.efajcgbm3qd2sam5@redhat.com> From: Vladimir Sementsov-Ogievskiy Message-ID: <07e2d433-766a-4a46-44f2-a8e19729c04d@virtuozzo.com> Date: Fri, 24 Sep 2021 00:50:41 +0300 User-Agent: Mozilla/5.0 (X11; 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envelope-from=vsementsov@virtuozzo.com; helo=EUR05-DB8-obe.outbound.protection.outlook.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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" 23.09.2021 23:33, Eric Blake wrote: > On Fri, Sep 03, 2021 at 01:28:03PM +0300, Vladimir Sementsov-Ogievskiy wrote: >> We are generally moving to int64_t for both offset and bytes parameters >> on all io paths. >> >> Main motivation is realization of 64-bit write_zeroes operation for >> fast zeroing large disk chunks, up to the whole disk. >> >> We chose signed type, to be consistent with off_t (which is signed) and >> with possibility for signed return type (where negative value means >> error). >> >> So, convert driver write_zeroes handlers bytes parameter to int64_t. >> >> The only caller of all updated function is bdrv_co_do_pwrite_zeroes(). >> >> bdrv_co_do_pwrite_zeroes() itself is of course OK with widening of >> callee parameter type. Also, bdrv_co_do_pwrite_zeroes()'s >> max_write_zeroes is limited to INT_MAX. So, updated functions all are >> safe, they will not get "bytes" larger than before. >> >> Still, let's look through all updated functions, and add assertions to >> the ones which are actually unprepared to values larger than INT_MAX. >> For these drivers also set explicit max_pwrite_zeroes limit. >> > [snip] >> >> At this point all block drivers are prepared to support 64bit >> write-zero requests, or have explicitly set max_pwrite_zeroes. > > The long commit message is essential, but the analysis looks sane. > >> >> Signed-off-by: Vladimir Sementsov-Ogievskiy >> --- > >> +++ b/block/iscsi.c > >> @@ -1250,11 +1250,21 @@ coroutine_fn iscsi_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset, >> iscsi_co_init_iscsitask(iscsilun, &iTask); >> retry: >> if (use_16_for_ws) { >> + /* >> + * iscsi_writesame16_task num_blocks argument is uint32_t. We rely here >> + * on our max_pwrite_zeroes limit. >> + */ >> + assert(nb_blocks < UINT32_MAX); >> iTask.task = iscsi_writesame16_task(iscsilun->iscsi, iscsilun->lun, lba, >> iscsilun->zeroblock, iscsilun->block_size, >> nb_blocks, 0, !!(flags & BDRV_REQ_MAY_UNMAP), >> 0, 0, iscsi_co_generic_cb, &iTask); > > Should this be <= instead of < ? > >> } else { >> + /* >> + * iscsi_writesame10_task num_blocks argument is uint16_t. We rely here >> + * on our max_pwrite_zeroes limit. >> + */ >> + assert(nb_blocks < UINT16_MAX); >> iTask.task = iscsi_writesame10_task(iscsilun->iscsi, iscsilun->lun, lba, >> iscsilun->zeroblock, iscsilun->block_size, >> nb_blocks, 0, !!(flags & BDRV_REQ_MAY_UNMAP), > > here too. The 16-bit limit is where we're most likely to run into > someone actually trying to zeroize that much at once. > >> +++ b/block/nbd.c >> @@ -1407,15 +1407,17 @@ static int nbd_client_co_pwritev(BlockDriverState *bs, int64_t offset, >> } >> >> static int nbd_client_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset, >> - int bytes, BdrvRequestFlags flags) >> + int64_t bytes, BdrvRequestFlags flags) >> { >> BDRVNBDState *s = (BDRVNBDState *)bs->opaque; >> NBDRequest request = { >> .type = NBD_CMD_WRITE_ZEROES, >> .from = offset, >> - .len = bytes, >> + .len = bytes, /* .len is uint32_t actually */ >> }; >> >> + assert(bytes < UINT32_MAX); /* relay on max_pwrite_zeroes */ > > And again. Here, you happen to get by with < because we clamped > bl.max_pwrite_zeroes at BDRV_REQUEST_MAX_BYTES, which is INT_MAX > rounded down. But I had to check; whereas using <= would be less > worrisome, even if we never get a request that large. > > If you agree with my analysis, I can make that change while preparing > my pull request. I agree, <= should be right thing, thanks! > > Reviewed-by: Eric Blake > -- Best regards, Vladimir