Hello, Atsushi. 2012/12/12 Atsushi Kumagai <kumagai-atsushi@xxxxxxxxxxxxxxxxx>: > Hello, > > On Tue, 11 Dec 2012 17:17:05 -0500 (EST) > Dave Anderson <anderson@xxxxxxxxxx> wrote: > >> >> >> ----- Original Message ----- >> > On Mon, Dec 10, 2012 at 11:40:47PM +0900, JoonSoo Kim wrote: >> > >> > [..] >> > > > So without knowing details of both the data structures, I think if vmlist >> > > > is going away, then user space tools should be able to traverse vmap_area_root >> > > > rb tree. I am assuming it is sorted using ->addr field and we should be >> > > > able to get vmalloc area start from there. It will just be a matter of >> > > > exporting right fields to user space (instead of vmlist). >> > > >> > > There is address sorted list of vmap_area, vmap_area_list. >> > > So we can use it for traversing vmalloc areas if it is necessary. >> > > But, as I mentioned before, kexec write *just* address of vmlist and >> > > offset of vm_struct's address field. It imply that they don't traverse vmlist, >> > > because they didn't write vm_struct's next field which is needed for traversing. >> > > Without vm_struct's next field, they have no method for traversing. >> > > So, IMHO, assigning dummy vm_struct to vmlist which is implemented by [7/8] is >> > > a safe way to maintain a compatibility of userspace tool. :) >> > >> > Actually the design of "makedumpfile" and "crash" tool is that they know >> > about kernel data structures and they adopt to changes. So for major >> > changes they keep track of kernel version numbers and if access the >> > data structures accordingly. >> > >> > Currently we access first element of vmlist to determine start of vmalloc >> > address. True we don't have to traverse the list. >> > >> > But as you mentioned we should be able to get same information by >> > traversing to left most element of vmap_area_list rb tree. So I think >> > instead of trying to retain vmlist first element just for backward >> > compatibility, I will rather prefer get rid of that code completely >> > from kernel and let user space tool traverse rbtree. Just export >> > minimum needed info for traversal in user space. >> >> There's no need to traverse the rbtree. There is a vmap_area_list >> linked list of vmap_area structures that is also sorted by virtual >> address. >> >> All that makedumpfile would have to do is to access the first vmap_area >> in the vmap_area_list -- as opposed to the way that it does now, which is >> by accessing the first vm_struct in the to-be-obsoleted vmlist list. >> >> So it seems silly to keep the dummy "vmlist" around. > > I think so, I will modify makedumpfile to get the start address of vmalloc > with vmap_area_list if the related symbols are provided as VMCOREINFO like > vmlist. > BTW, have we to consider other tools ? > If it is clear, I think we can get rid of the dummy vmlist. Good! In next spin, I will remove dummy vmlist and export vmap_area_list symbol for makedumpfile. I don't know any other tools. If anyone knows it, please let me know. Thanks! Atsushi, Dave and Vivek. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>