Commit 849b94c0 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Tong Tiangen
Browse files

mm: call wp_page_copy() under the VMA lock 

mainline inclusion
from mainline-v6.7-rc1
commit 164b06f238b986317131e6b61b2f22aabcbc2cc0
category: other
bugzilla: https://gitee.com/openeuler/kernel/issues/I8K7C7

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=164b06f238b986317131e6b61b2f22aabcbc2cc0

--------------------------------

It is usually safe to call wp_page_copy() under the VMA lock.  The only
unsafe situation is when no anon_vma has been allocated for this VMA, and
we have to look at adjacent VMAs to determine if their anon_vma can be
shared.  Since this happens only for the first COW of a page in this VMA,
the majority of calls to wp_page_copy() do not need to fall back to the
mmap_sem.

Add vmf_anon_prepare() as an alternative to anon_vma_prepare() which will
return RETRY if we currently hold the VMA lock and need to allocate an
anon_vma.  This lets us drop the check in do_wp_page().

Link: https://lkml.kernel.org/r/20231006195318.4087158-3-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarSuren Baghdasaryan <surenb@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarTong Tiangen <tongtiangen@huawei.com>
parent 9f2254c4

mm/memory.c

+26 −13
Original line number Diff line number Diff line
@@ -3044,6 +3044,21 @@ static inline void wp_page_reuse(struct vm_fault *vmf, struct folio *folio) 
	count_vm_event(PGREUSE);

}



static vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)

{

	struct vm_area_struct *vma = vmf->vma;



	if (likely(vma->anon_vma))

		return 0;

	if (vmf->flags & FAULT_FLAG_VMA_LOCK) {

		vma_end_read(vma);

		return VM_FAULT_RETRY;

	}

	if (__anon_vma_prepare(vma))

		return VM_FAULT_OOM;

	return 0;

}



/*

 * Handle the case of a page which we actually need to copy to a new page,

 * either due to COW or unsharing.
@@ -3071,27 +3086,29 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) 
	pte_t entry;

	int page_copied = 0;

	struct mmu_notifier_range range;

	int ret;

	vm_fault_t ret;



	delayacct_wpcopy_start();



	if (vmf->page)

		old_folio = page_folio(vmf->page);

	if (unlikely(anon_vma_prepare(vma)))

		goto oom;

	ret = vmf_anon_prepare(vmf);

	if (unlikely(ret))

		goto out;



	if (is_zero_pfn(pte_pfn(vmf->orig_pte))) {

		new_folio = vma_alloc_zeroed_movable_folio(vma, vmf->address);

		if (!new_folio)

			goto oom;

	} else {

		int err;

		new_folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma,

				vmf->address, false);

		if (!new_folio)

			goto oom;



		ret = __wp_page_copy_user(&new_folio->page, vmf->page, vmf);

		if (ret) {

		err = __wp_page_copy_user(&new_folio->page, vmf->page, vmf);

		if (err) {

			/*

			 * COW failed, if the fault was solved by other,

			 * it's fine. If not, userspace would re-fault on
@@ -3104,7 +3121,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) 
				folio_put(old_folio);



			delayacct_wpcopy_end();

			return ret == -EHWPOISON ? VM_FAULT_HWPOISON : 0;

			return err == -EHWPOISON ? VM_FAULT_HWPOISON : 0;

		}

		kmsan_copy_page_meta(&new_folio->page, vmf->page);

	}
@@ -3214,11 +3231,13 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) 
oom_free_new:

	folio_put(new_folio);

oom:

	ret = VM_FAULT_OOM;

out:

	if (old_folio)

		folio_put(old_folio);



	delayacct_wpcopy_end();

	return VM_FAULT_OOM;

	return ret;

}



/**
@@ -3444,12 +3463,6 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) 
		return 0;

	}

copy:

	if ((vmf->flags & FAULT_FLAG_VMA_LOCK) && !vma->anon_vma) {

		pte_unmap_unlock(vmf->pte, vmf->ptl);

		vma_end_read(vmf->vma);

		return VM_FAULT_RETRY;

	}



	/*

	 * Ok, we need to copy. Oh, well..

	 */