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<p class="MsoNormal"><span style="font-family:"Courier New"">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">I was setting up for some dm-cache testing this weekend (using 3.9.0-rc7 x86_64) and ran into the following:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""># dmsetup create cache --table '0 41943040 cache /dev/mapper/metadata /dev/mapper/ssd /dev/mapper/origin 512 1 writeback default 0'<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">device-mapper: reload ioctl on cache failed: Block device required<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Command failed<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">#<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">After this error, /var/log/messages contains:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">[75376.089354] device-mapper: cache metadata: sb_check failed: blocknr 18446744073709551615: wanted 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">[75376.089362] device-mapper: block manager: superblock validator check failed for block 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">[75376.089364] device-mapper: cache metadata: couldn't read lock superblock<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">[75376.095173] device-mapper: table: 253:5: cache: Error creating metadata object<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">[75376.095180] device-mapper: ioctl: error adding target to table<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">This comes from sb_check() in drivers/md/dm-cache-metadata.c and drivers/md/dm-thin-metadata.c, and it motivated me to try:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""># dd if=/dev/zero of=/dev/mapper/metadata bs=4k conv=notrunc<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Afterwards, I tried “dmsetup create cache” again and it worked fine.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Morgan Mears<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
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