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Wed, 5 May 2021 16:05:35 -0400 Received: from localhost (mpatocka@localhost) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4/Submit) with ESMTP id 145K5Z53006322; Wed, 5 May 2021 16:05:35 -0400 X-Authentication-Warning: file01.intranet.prod.int.rdu2.redhat.com: mpatocka owned process doing -bs Date: Wed, 5 May 2021 16:05:35 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Melvin Vermeeren In-Reply-To: <2912930.OmXdaqUpTP@verm-r4e> Message-ID: References: <6810395.sd9NxXGo4T@verm-r4e> <2912930.OmXdaqUpTP@verm-r4e> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-loop: dm-devel@redhat.com Cc: Mike Snitzer , dm-devel@redhat.com, Milan Broz Subject: Re: [dm-devel] [PATCH v2] dm-integrity: if we have discard support, use it when recalculating X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Wed, 5 May 2021, Melvin Vermeeren wrote: > Hi, > > On Wednesday, 5 May 2021 20:48:47 CEST Mikulas Patocka wrote: > > It doesn't matter if the device is discarded or not. If the metadata > > constains the discard filler, dm-integrity won't check the checksum - so > > the data can contain anything. > > > > ... > > > > The device after discard may contain random pattern (some SSDs really do) > > - so when the metadata contains the discard filler, the data may contain > > anything. > > So if an existing SSD is formatted with --no-wipe --data-device option and > then opened with --integrity-recalculate all metadata will contain the discard > filler with this patch. > > So then, all the current data in the drive is not checked for integrity > because it contains discard filler. This means that integrity recalculation > itself never takes place for existing data. Meaning that only newly written > data to SSD device will actually have integrity protection. > > Is this correct? Yes. Mikulas > Cheers, > > -- > Melvin Vermeeren > Systems engineer -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel