<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Jun 28, 2015 at 8:21 AM, Gili B <span dir="ltr"><<a href="mailto:gilib123@hotmail.com" target="_blank">gilib123@hotmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div dir="ltr">hi<br>We are starting working on a new device mapper module which has targets similar<br>to the ones in thin module (pool and thin), but it adds some additional features.<br>The user should be able to create and use file systems on the thin volumes.<br>I wanted to know what is the recommended way to make the configuration with dmsetup<br>persistent ?<br></div></div></blockquote><div><br><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline">You should probably use mdraid as an inspiration. Put a signature block on every member device. You can then write a user-space tool to scan devices and find the collections. Be sure to use a good "signature" for your type of device, plus a good UUID signature so that different generations can be identified.<br></div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div dir="ltr">We want that all file systems will be available after reboot.<br></div></div></blockquote><div><br><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline">If you get the device running early enough, then fstab should be able to mount file systems.<br></div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div dir="ltr">Should we write our own configuration tool? should we add special configuration files?<br></div></div></blockquote><div><br><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline">You will probably need a user-space tool. You can probably get away with no configuration file, but you should again use mdraid as inspiration so that your user-space tool gets limits of where to look for member pieces.<br></div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div dir="ltr">Should the kernel module we write , automatically discover all the configration and initialize accordingly?<br> <br> <br>Regarding debug - Is there a generic way to run dmsetup for example that<br>prints some inside details on the targets? (for example number of outstanding ios, memory used etc)<br></div></div></blockquote><div><br><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline">You can do this three ways. 1) build in IOCTL into your module that can query stuff. 2) export stuff in /sys. 3) export stuff in /proc. I personally like exporting debug stuff into /proc. Remember that printk is your friend. I have even created "command" file in proc that then dump debug information with printk. If you use /proc, you need to handle multiple instances of your mapper. I use /proc/{my_project_name}/{instance_name}/...<br></div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div dir="ltr"> <br> <br>Thanks<span class="HOEnZb"><font color="#888888"><br>-gili<br> </font></span></div></div>
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