Handle a little more of the page fault path outside the mmap sem. The hugetlb path doesn't need to check whether the VMA is anonymous; the VM_HUGETLB flag is only set on hugetlbfs VMAs. There should be no performance change from the previous commit; this is simply a step to ease bisection of any problems. Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> --- mm/hugetlb.c | 4 ++++ mm/memory.c | 14 +++++++------- 2 files changed, 11 insertions(+), 7 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index efc443a906fa..39f168e3518f 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6052,6 +6052,10 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, int need_wait_lock = 0; unsigned long haddr = address & huge_page_mask(h); + /* TODO: Handle faults under the VMA lock */ + if (flags & FAULT_FLAG_VMA_LOCK) + return VM_FAULT_RETRY; + /* * Serialize hugepage allocation and instantiation, so that we don't * get spurious allocation failures if two CPUs race to instantiate diff --git a/mm/memory.c b/mm/memory.c index f726f85f0081..fc1f0ef9a7a5 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4992,10 +4992,10 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf) } /* - * By the time we get here, we already hold the mm semaphore - * - * The mmap_lock may have been released depending on flags and our - * return value. See filemap_fault() and __folio_lock_or_retry(). + * On entry, we hold either the VMA lock or the mmap_lock + * (FAULT_FLAG_VMA_LOCK tells you which). If VM_FAULT_RETRY is set in + * the result, the mmap_lock is not held on exit. See filemap_fault() + * and __folio_lock_or_retry(). */ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma, unsigned long address, unsigned int flags) @@ -5014,6 +5014,9 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma, p4d_t *p4d; vm_fault_t ret; + if ((flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vma)) + return VM_FAULT_RETRY; + pgd = pgd_offset(mm, address); p4d = p4d_alloc(mm, pgd, address); if (!p4d) @@ -5223,9 +5226,6 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, flags & FAULT_FLAG_REMOTE)) return VM_FAULT_SIGSEGV; - if ((flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vma)) - return VM_FAULT_RETRY; - /* * Enable the memcg OOM handling for faults triggered in user * space. Kernel faults are handled more gracefully. -- 2.39.2
