Commit 7f70c2a6 authored by Arjun Roy's avatar Arjun Roy Committed by Linus Torvalds
Browse files

mm/memory.c: properly pte_offset_map_lock/unlock in vm_insert_pages() 

Calls to pte_offset_map() in vm_insert_pages() are erroneously not
matched with a call to pte_unmap().  This would cause problems on
architectures where that is not a no-op.

This patch does away with the non-traditional locking in the existing
code, and instead uses pte_offset_map_lock/unlock() as usual,
incrementing PTE as necessary.  The PTE pointer is kept within bounds
since we clamp it with PTRS_PER_PTE.

Link: http://lkml.kernel.org/r/20200618220446.20284-1-arjunroy.kdev@gmail.com


Fixes: 8cd3984d ("mm/memory.c: add vm_insert_pages()")
Signed-off-by: default avatarArjun Roy <arjunroy@google.com>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 243bce09

mm/memory.c

+11 −10
Original line number Diff line number Diff line
@@ -1498,7 +1498,7 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr, 
}



#ifdef pte_index

static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd,

static int insert_page_in_batch_locked(struct mm_struct *mm, pte_t *pte,

			unsigned long addr, struct page *page, pgprot_t prot)

{

	int err;
@@ -1506,8 +1506,9 @@ static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd, 
	if (!page_count(page))

		return -EINVAL;

	err = validate_page_before_insert(page);

	return err ? err : insert_page_into_pte_locked(

		mm, pte_offset_map(pmd, addr), addr, page, prot);

	if (err)

		return err;

	return insert_page_into_pte_locked(mm, pte, addr, page, prot);

}



/* insert_pages() amortizes the cost of spinlock operations
@@ -1517,7 +1518,8 @@ static int insert_pages(struct vm_area_struct *vma, unsigned long addr, 
			struct page **pages, unsigned long *num, pgprot_t prot)

{

	pmd_t *pmd = NULL;

	spinlock_t *pte_lock = NULL;

	pte_t *start_pte, *pte;

	spinlock_t *pte_lock;

	struct mm_struct *const mm = vma->vm_mm;

	unsigned long curr_page_idx = 0;

	unsigned long remaining_pages_total = *num;
@@ -1536,18 +1538,17 @@ static int insert_pages(struct vm_area_struct *vma, unsigned long addr, 
	ret = -ENOMEM;

	if (pte_alloc(mm, pmd))

		goto out;

	pte_lock = pte_lockptr(mm, pmd);



	while (pages_to_write_in_pmd) {

		int pte_idx = 0;

		const int batch_size = min_t(int, pages_to_write_in_pmd, 8);



		spin_lock(pte_lock);

		for (; pte_idx < batch_size; ++pte_idx) {

			int err = insert_page_in_batch_locked(mm, pmd,

		start_pte = pte_offset_map_lock(mm, pmd, addr, &pte_lock);

		for (pte = start_pte; pte_idx < batch_size; ++pte, ++pte_idx) {

			int err = insert_page_in_batch_locked(mm, pte,

				addr, pages[curr_page_idx], prot);

			if (unlikely(err)) {

				spin_unlock(pte_lock);

				pte_unmap_unlock(start_pte, pte_lock);

				ret = err;

				remaining_pages_total -= pte_idx;

				goto out;
@@ -1555,7 +1556,7 @@ static int insert_pages(struct vm_area_struct *vma, unsigned long addr, 
			addr += PAGE_SIZE;

			++curr_page_idx;

		}

		spin_unlock(pte_lock);

		pte_unmap_unlock(start_pte, pte_lock);

		pages_to_write_in_pmd -= batch_size;

		remaining_pages_total -= batch_size;

	}