Due to the rebase to latest rc6, the major pte copy patch changed a lot. So maybe not that useful to write a changelog any more. However all the comments should be addressed as long as discussed in previous thread. Please shoot if I missed anything important. This series is majorly inspired by the previous discussion on the list [1], starting from the report from Jason on the rdma test failure. Linus proposed the solution, which seems to be a very nice approach to avoid the breakage of userspace apps that didn't use MADV_DONTFORK properly before. More information can be found in that thread too. I tested it myself with fork() after vfio pinning a bunch of device pages, and I verified that the new copy pte logic worked as expected at least in the most general path. However I didn't test thp case yet because afaict vfio does not support thp backed dma pages. Luckily, the pmd/pud thp patch is much more straightforward than the pte one, so hopefully it can be directly verified by some code review plus some more heavy-weight rdma tests. Patch 1: Introduce mm.has_pinned Patch 2: Preparation patch Patch 3: Early cow solution for pte copy for pinned pages Patch 4: Same as above, but for thp (pmd/pud). Hugetlbfs fix is still missing, but as planned, that's not urgent so we can work upon. Comments greatly welcomed. [1] https://lore.kernel.org/lkml/20200914143829.GA1424636@xxxxxxxxxx/ Thanks. Peter Xu (4): mm: Introduce mm_struct.has_pinned mm/fork: Pass new vma pointer into copy_page_range() mm: Do early cow for pinned pages during fork() for ptes mm/thp: Split huge pmds/puds if they're pinned when fork() include/linux/mm.h | 2 +- include/linux/mm_types.h | 10 +++ kernel/fork.c | 3 +- mm/gup.c | 6 ++ mm/huge_memory.c | 28 ++++++ mm/memory.c | 186 ++++++++++++++++++++++++++++++++++----- 6 files changed, 212 insertions(+), 23 deletions(-) -- 2.26.2
