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bh=UQxGloWJPoL35y+LCeC8eZ1y74KFxCNhy3YU7t10Q/A=; b=HU9WAw6qQdAX++dYLX+gPBwwTOEx1kv836ogB54aoTQqxQLPp5jDLri1VimYPnn7STDp+G iD8V319/2VgSjRwV2sI2h+sTIBUxkgcG93To47SIPZqs09RNCSWANd9h0Gs31fFxrrsMkz 5cYlaIZ263gw6YlMwTcZq3Fn9TzR+BY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-321-DDKCub2vOwSwunigQuIC7w-1; Thu, 23 Sep 2021 16:33:57 -0400 X-MC-Unique: DDKCub2vOwSwunigQuIC7w-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D839EA40C0; Thu, 23 Sep 2021 20:33:55 +0000 (UTC) Received: from redhat.com (ovpn-115-8.phx2.redhat.com [10.3.115.8]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7AD0460BE5; Thu, 23 Sep 2021 20:33:47 +0000 (UTC) Date: Thu, 23 Sep 2021 15:33:45 -0500 From: Eric Blake To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH v6 07/11] block: use int64_t instead of int in driver write_zeroes handlers Message-ID: <20210923203345.efajcgbm3qd2sam5@redhat.com> References: <20210903102807.27127-1-vsementsov@virtuozzo.com> <20210903102807.27127-8-vsementsov@virtuozzo.com> MIME-Version: 1.0 In-Reply-To: <20210903102807.27127-8-vsementsov@virtuozzo.com> User-Agent: NeoMutt/20210205-773-8890a5 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.473, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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: , Cc: fam@euphon.net, kwolf@redhat.com, integration@gluster.org, berto@igalia.com, stefanha@redhat.com, qemu-block@nongnu.org, pavel.dovgaluk@ispras.ru, sw@weilnetz.de, pl@kamp.de, qemu-devel@nongnu.org, jsnow@redhat.com, hreitz@redhat.com, kraxel@redhat.com, ronniesahlberg@gmail.com, pbonzini@redhat.com, idryomov@gmail.com, philmd@redhat.com, ari@tuxera.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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. Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org