Hello Matthew, Hope you are doing well. I am Chaitanya from the linux graphics team in Intel. This mail is regarding a regression we are seeing in our CI runs[1] on linux-next repository. Since the version next-20240228 [2], we are seeing the following regression ````````````````````````````````````````````````````````````````````````````````` <6> [388.274691] i915: Running intel_migrate_live_selftests/live_migrate_copy <7> [388.274790] i915 0000:00:02.0: [drm:gsc_work [i915]] GT1: GSC Proxy initialized <4> [388.540070] page:ffffea0004666880 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1199a2 <4> [388.540111] flags: 0x8000000000000000(zone=2) <4> [388.540117] page_type: 0xffffffff() <4> [388.540123] raw: 8000000000000000 ffffea0004524008 ffffea0005f68e08 0000000000000000 <4> [388.540127] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 <4> [388.540130] page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0) <4> [388.540140] ------------[ cut here ]------------ <2> [388.540143] kernel BUG at include/linux/mm.h:1134! <4> [388.544999] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI <4> [388.550187] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G U 6.8.0-rc6-next-20240228-next-20240228-g20af1ca418d2+ #1 <4> [388.561471] Hardware name: Intel Corporation Meteor Lake Client Platform/MTL-P DDR5 SODIMM SBS RVP, BIOS MTLPFWI1.R00.3471.D91.2401310918 01/31/2024 <4> [388.574636] RIP: 0010:put_pages_list+0x92/0xe0 ````````````````````````````````````````````````````````````````````````````````` Details log can be found in [3]. After bisecting the tree, the following patch [4] seems to be the first "bad" commit ````````````````````````````````````````````````````````````````````````````````````````````````````````` commit ac7130117e8860081be88149061b5abb654d5759 Author: Matthew Wilcox (Oracle) mailto:willy@xxxxxxxxxxxxx Date: Tue Feb 27 17:42:41 2024 +0000 mm: use free_unref_folios() in put_pages_list() Break up the list of folios into batches here so that the folios are more likely to be cache hot when doing the rest of the processing. Link: https://lkml.kernel.org/r/20240227174254.710559-8-willy@xxxxxxxxxxxxx Signed-off-by: Matthew Wilcox (Oracle) mailto:willy@xxxxxxxxxxxxx ````````````````````````````````````````````````````````````````````````````````````````````````````````` We could not revert the patch because of a build errors but resetting to the parent of the commit seems to fix the issue Could you please check why the patch causes this regression and provide a fix if necessary? Thank you. Regards Chaitanya [1] https://intel-gfx-ci.01.org/tree/linux-next/combined-alt.html? [2] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20240228 [3] https://intel-gfx-ci.01.org/tree/linux-next/next-20240228/bat-mtlp-8/igt@i915_selftest@live@xxxxxxxxxxxx [4] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20240228&id=ac7130117e8860081be88149061b5abb654d5759
