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mm: move FAULT_FLAG_VMA_LOCK check from handle_mm_fault()

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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.

Link: https://lkml.kernel.org/r/20230724185410.1124082-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Arjun Roy <arjunroy@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Punit Agrawal <punit.agrawal@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2023-07-24 19:54:03 +01:00 committed by Andrew Morton
parent 350f6bbca1
commit 4ec31152a8
2 changed files with 15 additions and 9 deletions
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6
mm/hugetlb.c
View File

@ -6062,6 +6062,12 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
int need_wait_lock = 0; int need_wait_lock = 0;
unsigned long haddr = address & huge_page_mask(h); unsigned long haddr = address & huge_page_mask(h);
/* TODO: Handle faults under the VMA lock */
if (flags & FAULT_FLAG_VMA_LOCK) {
vma_end_read(vma);
return VM_FAULT_RETRY;
}
/* /*
* Serialize hugepage allocation and instantiation, so that we don't * Serialize hugepage allocation and instantiation, so that we don't
* get spurious allocation failures if two CPUs race to instantiate * get spurious allocation failures if two CPUs race to instantiate

18
mm/memory.c
View File

@ -4984,10 +4984,10 @@ unlock:
} }
/* /*
* By the time we get here, we already hold the mm semaphore * 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 mmap_lock may have been released depending on flags and our * the result, the mmap_lock is not held on exit. See filemap_fault()
* return value. See filemap_fault() and __folio_lock_or_retry(). * and __folio_lock_or_retry().
*/ */
static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma, static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
unsigned long address, unsigned int flags) unsigned long address, unsigned int flags)
@ -5006,6 +5006,11 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
p4d_t *p4d; p4d_t *p4d;
vm_fault_t ret; vm_fault_t ret;
if ((flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vma)) {
vma_end_read(vma);
return VM_FAULT_RETRY;
}
pgd = pgd_offset(mm, address); pgd = pgd_offset(mm, address);
p4d = p4d_alloc(mm, pgd, address); p4d = p4d_alloc(mm, pgd, address);
if (!p4d) if (!p4d)
@ -5222,11 +5227,6 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
goto out; goto out;
} }
if ((flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vma)) {
vma_end_read(vma);
return VM_FAULT_RETRY;
}
/* /*
* Enable the memcg OOM handling for faults triggered in user * Enable the memcg OOM handling for faults triggered in user
* space. Kernel faults are handled more gracefully. * space. Kernel faults are handled more gracefully.