Thanks for reply, you are right, there may be something still holds a reference of that, which also cause the device busy after 'dmsetup remove'. I figure out the reason is that, there is one "divide error" which may crash device mapper, I just do not expect that is the reason why destruction of target never got invoked. Thanks very much. Alan <div class="gmail_quote">2008/11/9 Alasdair G Kergon <<a href="mailto:agk@redhat.com">agk@redhat.com</a>> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> <div class="Ih2E3d">On Sun, Nov 09, 2008 at 12:27:24AM -0500, Reng Zeng wrote: > However, I use "dmsetup remove" hundreds times, as the debug info, but it > never enter the dtr function I defined. > Anybody have idea on this? Or how to dig into that to discover the reason? </div>Something still holds a reference to the table? E.g. you have dm_table_get() without a matching dm_table_put() somewhere. Try a debugger like kgdb? Check t->holders? Or post your code here (assuming it's GPL) and someone might help. Alasdair -- <a href="mailto:agk@redhat.com">agk@redhat.com</a> -- 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>