Hi Malahal Is there any way to find the last sector of bio. Is this a correct way to find last sector of bio "bio->bi_sector=bio->bi_sector + (bio->bi_size >> 9)-1" or bio_for_each_segment(bvec,bio,<div id=":1ae">idx) { bio->bi_sector=bio->bi_sector + (bvec->bv_len >> 9) -1; } Actually what i think both are same thing but in different way. Will this bio->bi_sector point to last sector of bio if bio->bi_vcnt is greater than 1. What is correct way to find/get last sector from bio? Regards, Nishant.</div> <div class="gmail_quote">On Fri, Jan 28, 2011 at 2:42 PM, Malahal Naineni <<a href="mailto:malahal@us.ibm.com">malahal@us.ibm.com</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> <div><div></div><div class="h5">nishant mungse [<a href="mailto:nishantmungse@gmail.com">nishantmungse@gmail.com</a>] wrote: > Hi, > > I've created a device mapper target and I wanna test its read and > write mechanisms. I created a device using this target and tried to > write a filesystem on to the device. > > My target is creating roughly two outgoing bios per incoming bio. > Which is maybe why I'm not able to get a proper log after running the > mke2fs command as while writing the filesystem, there are massive > amounts of writes performed on the device. > > So, I tried to use the cat command to directly write to the device > file. The write is being performed for sure because I'm able to view > the data written to the underlying device. > > But there is no output when I try to read the device file contents using cat. > > Is there any other way to test the read/write workflows of a dm target > that can give out a proper log ? </div></div>I am not sure what you mean by 'proper log'. I would use 'dd' with direct I/O to avoid cache so that every read and write directly go to the device. I don't think you can do that with 'cat' command. -- dm-devel mailing list <a href="mailto:dm-devel@redhat.com">dm-devel@redhat.com</a> <a href="https://www.redhat.com/mailman/listinfo/dm-devel" target="_blank">https://www.redhat.com/mailman/listinfo/dm-devel</a> </blockquote></div>