[Based on mm-unstable, commit a53138cdbe3e] Dax supports pud pages for a while, but mprotect on puds was missing since the start. This series tries to fix that by providing pud handling in mprotect(), while my real goal is adding more types of pud mappings like hugetlb or pfnmaps, it's just that we probably want pud to work already and build the rest on top. Considering nobody reported this until when I looked at those other types of pud mappings, I am thinking maybe it doesn't need to be a fix for stable and this may not need to be backported. I would guess whoever cares about mprotect() won't care 1G dax puds yet, vice versa. I hope fixing that in new kernels would be fine, but I'm open to suggestions. There're quite a few small things changed here and there to teach mprotect work on PUDs. E.g. it will start with dropping NUMA_HUGE_PTE_UPDATES which may stop making much sense when there can be more than one type of huge pte (meanwhile it doesn't sound right at all to account non-numa operations too.. more in the commit message of the relevant patch). OTOH, we'll also need to push the mmu notifiers from pmd to pud layers, which might need some attention but so far I think it's safe. For these small details, please refer to each patch's commit message. The mprotect() pud process is hopefully straightforward enough, as I kept it as simple as possible. There's no NUMA handled as dax simply doesn't support that. There's also no userfault involvements as file memory (even if work with userfault-wp async mode) will need to split a pud, so pud entry doesn't need to yet know userfault's existance (but hugetlb entries will; that's also for later). Tests ===== What I did test: - cross-build tests that I normally cover [1], except an known issue elsewhere on hugetlb [2] - smoke tested on x86_64 the simplest program [3] on dev_dax 1G PUD mprotect() using QEMU's nvdimm emulations [4] and ndctl to create namespaces with proper alignments, which used to throw "bad pud" but now it'll run through all fine. Also I checked sigbus happens if with illegal access on protected puds. What I didn't test: - fsdax: I wanted to also give it a shot, but only until then I noticed it doesn't seem to be supported (according to dax_iomap_fault(), which will always fallback on PUD_ORDER). I did remember it was supported before, I could miss something important there.. please shoot if so. - userfault wp-async: I also wanted to test userfault-wp async be able to split huge puds (here it's simply a clear_pud.. though), but it won't work for devdax anyway due to not allowed to do smaller than 1G faults in this case. So skip too. - Power, as no hardware on hand. Thanks, [1] https://gitlab.com/peterx/lkb-harness/-/blob/main/config.json [2] https://lore.kernel.org/all/202406190956.9j1UCIe5-lkp@xxxxxxxxx [2] https://github.com/xzpeter/clibs/blob/master/misc/dax.c [3] https://github.com/qemu/qemu/blob/master/docs/nvdimm.txt Peter Xu (7): mm/dax: Dump start address in fault handler mm/mprotect: Remove NUMA_HUGE_PTE_UPDATES mm/mprotect: Push mmu notifier to PUDs mm/powerpc: Add missing pud helpers mm/x86: Make pud_leaf() only cares about PSE bit mm/x86: Add missing pud helpers mm/mprotect: fix dax pud handlings arch/powerpc/include/asm/book3s/64/pgtable.h | 3 + arch/powerpc/mm/book3s64/pgtable.c | 20 ++++++ arch/x86/include/asm/pgtable.h | 39 ++++++++++- arch/x86/mm/pgtable.c | 11 +++ drivers/dax/device.c | 6 +- include/linux/huge_mm.h | 24 +++++++ include/linux/vm_event_item.h | 1 - mm/huge_memory.c | 52 ++++++++++++++ mm/mprotect.c | 74 ++++++++++++-------- mm/vmstat.c | 1 - 10 files changed, 195 insertions(+), 36 deletions(-) -- 2.45.0
