v4: - add r-b for Mike on the last patch, add some more commit message explains that why we don't need wr-protect trick - fix one warning of unused var in copy_present_page() [Gal] v3: - rebase to linux-next/akpm, switch to the new HPAGE helpers [MikeK] - correct error check for alloc_huge_page(); test it this time to make sure fork() fails gracefully when overcommit [MikeK] - move page copy out of pgtable lock: this changed quite a bit of the logic in the last patch, prealloc is dropped since I found it easier to understand without looping at all [MikeK] v2: - pass in 1 to alloc_huge_page() last param [Mike] - reduce comment, unify the comment in one place [Linus] - add r-bs for Mike and Miaohe ---- original cover letter ---- As reported by Gal [1], we still miss the code clip to handle early cow for hugetlb case, which is true. Again, it still feels odd to fork() after using a few huge pages, especially if they're privately mapped to me.. However I do agree with Gal and Jason in that we should still have that since that'll complete the early cow on fork effort at least, and it'll still fix issues where buffers are not well under control and not easy to apply MADV_DONTFORK. The first two patches (1-2) are some cleanups I noticed when reading into the hugetlb reserve map code. I think it's good to have but they're not necessary for fixing the fork issue. The last two patches (3-4) is the real fix. I tested this with a fork() after some vfio-pci assignment, so I'm pretty sure the page copy path could trigger well (page will be accounted right after the fork()), but I didn't do data check since the card I assigned is some random nic. Gal, please feel free to try this if you have better way to verify the series. https://github.com/xzpeter/linux/tree/fork-cow-pin-huge Please review, thanks! [1] https://lore.kernel.org/lkml/27564187-4a08-f187-5a84-3df50009f6ca@xxxxxxxxxx/ Peter Xu (5): hugetlb: Dedup the code to add a new file_region hugetlg: Break earlier in add_reservation_in_range() when we can mm: Introduce page_needs_cow_for_dma() for deciding whether cow mm: Use is_cow_mapping() across tree where proper hugetlb: Do early cow when page pinned on src mm drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c | 4 +- drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c | 2 +- fs/proc/task_mmu.c | 2 - include/linux/mm.h | 21 ++++ mm/huge_memory.c | 8 +- mm/hugetlb.c | 123 +++++++++++++++------ mm/internal.h | 5 - mm/memory.c | 8 +- 8 files changed, 117 insertions(+), 56 deletions(-) -- 2.26.2
