On 1/3/23 14:46, Oliver Sang wrote: > hi, > >> >> Yet the page owner info tells us, 0x2daee was most recently used as order-1, >> and now it seems to be (based on the raw struct page dump) sitting on a pcplist. >> >> So the events leading up to this could be something like: >> >> - 0x2daee is order-1 slab folio of the inode cache, sitting on the partial list >> - despite being on partial list, it's freed ??? >> - somebody else allocates order-2 page 0x2daec and uses it for whatever, >> then frees it >> - 0x2daec is reallocated as order-1 slab from names_cache, then freed >> - we try to allocate from the slab page 0x2daee and trip on the PageTail >> >> Except, the freeing of order-2 page would have reset the PageTail and >> compound_head in 0x2daec, so this is even more complicated or involves some >> extra race? > > FYI, we ran tests more up to 500 times, then saw different issues but rate is > actually low > > 56d5a2b9ba85a390 0af8489b0216fa1dd83e264bef8 > ---------------- --------------------------- > fail:runs %reproduction fail:runs > | | | > :500 12% 61:500 dmesg.invalid_opcode:#[##] > :500 3% 14:500 dmesg.kernel_BUG_at_include/linux/mm.h > :500 3% 17:500 dmesg.kernel_BUG_at_include/linux/page-flags.h > :500 5% 26:500 dmesg.kernel_BUG_at_lib/list_debug.c > :500 0% 2:500 dmesg.kernel_BUG_at_mm/page_alloc.c > :500 0% 2:500 dmesg.kernel_BUG_at_mm/usercopy.c Hm even if rate is low, the different kinds of reports could be useful to see, if all of that is caused by the commit. >> >> In any case, this is something a debug_pagealloc kernel could have a chance >> of catching earlier. Would it be possible to enable CONFIG_DEBUG_PAGEALLOC >> and DEBUG_PAGEALLOC_ENABLE_DEFAULT additionally to the rest of the >> configuration, and repeat the test? > > ok, we are starting to test by these 2 additional configs now. Great, thanks!
