On Fri, May 10, 2024 at 11:07:11AM +0800, Kuan-Wei Chiu wrote: > On Thu, May 09, 2024 at 07:16:31PM -0400, Kent Overstreet wrote: > > On Fri, May 10, 2024 at 06:44:29AM +0800, Kuan-Wei Chiu wrote: > > > On Thu, May 09, 2024 at 03:58:57PM -0400, Kent Overstreet wrote: > > > > On Thu, May 09, 2024 at 03:27:45PM +1000, Stephen Rothwell wrote: > > > > > Hi all, > > > > > > > > > > Today's linux-next merge of the refactor-heap tree got conflicts in: > > > > > > > > > > drivers/md/bcache/bset.c > > > > > drivers/md/bcache/bset.h > > > > > drivers/md/bcache/btree.c > > > > > drivers/md/bcache/writeback.c > > > > > > > > > > between commit: > > > > > > > > > > 3a861560ccb3 ("bcache: fix variable length array abuse in btree_iter") > > > > > > > > > > from the block tree and commit: > > > > > > > > > > afa5721abaaa ("bcache: Remove heap-related macros and switch to generic min_heap") > > > > > > > > > > from the refactor-heap tree. > > > > > > > > > > Ok, these conflicts are too extensive, so I am dropping the refactor-heap > > > > > tree for today. I suggest you all get together and sort something out. > > > > > > > > Coli and Kuan, you guys will need to get this sorted out quick if we > > > > want refactor-heap to make the merge window > > > > > > Hi Coli and Kent, > > > > > > If I understand correctly, the reported bug is because we attempted to > > > point (heap)->data to a dynamically allocated memory , but at that time > > > (heap)->data was not a regular pointer but a fixed size array with a > > > length of MAX_BSETS. > > > > > > In my refactor heap patch series, I introduced a preallocated array and > > > decided in min_heap_init() whether the data pointer should point to an > > > incoming pointer or to the preallocated array. Therefore, I am > > > wondering if my patch might have unintentionally fixed this bug? > > > > > > I am unsure how to reproduce the reported issue. Could you assist me in > > > verifying whether my assumption is correct? > > > > This is a merge conflict, not a runtime. Can you rebase onto Coli's > > tree? We'll have to retest. > > Oh, sorry for the misunderstanding I caused. When I mentioned "bug" [1] > earlier, I was referring to the bug addressed in > 3a861560ccb3 ("bcache: fix variable length array abuse in btree_iter"), > not a merge conflict. > > Here are the results after the rebase: > https://github.com/visitorckw/linux.git refactor-heap > > [1]: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2039368 The ubuntu kernels build with UBSAN now, and the bug reported is just a UBSAN warning. The original implementation's iterator has a fixed size sets array that is indexed out of bounds when the iterator is allocated on the heap with more space -- the patch restructures it a bit to have a single iterator type with a flexible array and then a larger "stack" type which embeds the iterator along with the preallocated region. I took a brief look at the refactor-heap branch but I'm not entirely sure what's going on with the new min heaps: in the one place where the larger iterators are used (in bch_btree_node_read_done) it doesn't look like the heap is ever initialized (perhaps since the old iter_init wasn't used here because of the special case it got missed in the refactor?) With the new heaps it should be fairly easy to fix though; just change the fill_iter mempool to be allocating only the minheap data arrays and setup iter->heap.data properly with that instead. Hope that helps, Matthew Mirvish > > Regards, > Kuan-Wei