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[140.113.168.124]) by smtp.googlemail.com with ESMTPSA id a3sm11463222pgd.73.2020.07.12.12.40.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Jul 2020 12:40:56 -0700 (PDT) From: Austin Chang To: dm-devel@redhat.com Cc: Austin Chang , Alasdair Kergon , Mike Snitzer , Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] dm-cache: document zeroing metadata device step Date: Mon, 13 Jul 2020 03:40:39 +0800 Message-Id: <20200712194039.329035-1-austin880625@gmail.com> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Inform dmsetup users to zero the first 4k of the metadata device at cache creation in examples, just as mentioned in thin-provisioning documentation. Instructions to use lvmcache for end users may be added as well. Link: https://www.redhat.com/archives/dm-devel/2013-April/msg00124.html Signed-off-by: Austin Chang --- Documentation/admin-guide/device-mapper/cache.rst | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/Documentation/admin-guide/device-mapper/cache.rst b/Documentation/admin-guide/device-mapper/cache.rst index f15e5254d05b..ef9a82d50d19 100644 --- a/Documentation/admin-guide/device-mapper/cache.rst +++ b/Documentation/admin-guide/device-mapper/cache.rst @@ -330,6 +330,10 @@ https://github.com/jthornber/device-mapper-test-suite :: + # When using dmsetup directly instead of volume manager like lvm2, + # the first 4k of the metadata device should be zeroed to indicate + # empty metadata. + dd if=/dev/zero of=/dev/mapper/metadata bs=4k conv=notrunc dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \ /dev/mapper/ssd /dev/mapper/origin 512 1 writeback default 0' dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \ -- 2.26.2