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mm: don't call vm_ops->huge_fault() in wp_huge_pmd()/wp_huge_pud() for private mappings 

If we already have a PMD/PUD mapped write-protected in a private mapping
and we want to break COW either due to FAULT_FLAG_WRITE or
FAULT_FLAG_UNSHARE, there is no need to inform the file system just like on
the PTE path.

Let's just split (->zap) + fallback in that case.

This is a preparation for more generic FAULT_FLAG_UNSHARE support in
COW mappings.

Link: https://lkml.kernel.org/r/20221116102659.70287-8-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2022-11-16 11:26:46 +01:00 committed by Andrew Morton
parent b9086fde6d
commit aea06577a9
1 changed files with 15 additions and 9 deletions
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24
mm/memory.c
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@ -4802,6 +4802,7 @@ static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf)
static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf)
{
const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
vm_fault_t ret;
if (vma_is_anonymous(vmf->vma)) {
if (likely(!unshare) &&
@ -4809,11 +4810,13 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf)
return handle_userfault(vmf, VM_UFFD_WP);
return do_huge_pmd_wp_page(vmf);
}
if (vmf->vma->vm_ops->huge_fault) {
vm_fault_t ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
if (vmf->vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) {
if (vmf->vma->vm_ops->huge_fault) {
ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
}
}
/* COW or write-notify handled on pte level: split pmd. */
@ -4839,14 +4842,17 @@ static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
{
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \
defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
vm_fault_t ret;
/* No support for anonymous transparent PUD pages yet */
if (vma_is_anonymous(vmf->vma))
goto split;
if (vmf->vma->vm_ops->huge_fault) {
vm_fault_t ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
if (vmf->vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) {
if (vmf->vma->vm_ops->huge_fault) {
ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
}
}
split:
/* COW or write-notify not handled on PUD level: split pud.*/