It is generally safe to handle hugetlb faults under the VMA lock. The only time this is unsafe is when no anon_vma has been allocated to this vma yet, so we can use vmf_anon_prepare() instead of anon_vma_prepare() to bailout if necessary. This should only happen for the first hugetlb page in the vma. Additionally, this patchset begins to use struct vm_fault within hugetlb_fault(). This works towards cleaning up hugetlb code, and should significantly reduce the number of arguments passed to functions. ----- The last patch in this series may cause ltp hugemmap10 to "fail". This is because vmf_anon_prepare() may bailout with no anon_vma under the VMA lock after allocating a folio for the hugepage. In free_huge_folio(), this folio is completely freed on bailout iff there is a surplus of hugetlb pages. This will remove a folio off the freelist and decrement the number of hugepages while ltp expects these counters to remain unchanged on failure. The rest of the ltp testcases pass. v2: - Removed unnecessary variables and indentations - Declare struct vm_fault in hugetlb_fault and pass it down as an argument instead of defining it in each called function. - Moved vmf_anon_prepare() declaration to mm/internal.h from include/linux/hugetlb.h Vishal Moola (Oracle) (5): mm/memory: Change vmf_anon_prepare() to be non-static hugetlb: Move vm_struct declaration to the top of hugetlb_fault() hugetlb: Pass struct vm_fault through to hugetlb_handle_userfault() hugetlb: Use vmf_anon_prepare() instead of anon_vma_prepare() hugetlb: Allow faults to be handled under the VMA lock mm/hugetlb.c | 88 ++++++++++++++++++++------------------------------- mm/internal.h | 1 + mm/memory.c | 2 +- 3 files changed, 36 insertions(+), 55 deletions(-) -- 2.43.0
