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Commit 93e478d4 authored by Shachar Raindel's avatar Shachar Raindel Committed by Linus Torvalds
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mm: refactor do_wp_page handling of shared vma into a function 



The do_wp_page function is extremely long.  Extract the logic for
handling a page belonging to a shared vma into a function of its own.

This helps the readability of the code, without doing any functional
change in it.

Signed-off-by: default avatarShachar Raindel <raindel@mellanox.com>
Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarAndi Kleen <ak@linux.intel.com>
Acked-by: default avatarHaggai Eran <haggaie@mellanox.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Peter Feiner <pfeiner@google.com>
Cc: Michel Lespinasse <walken@google.com>
Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2f38ab2c

mm/memory.c

+48 −38
Original line number Diff line number Diff line
@@ -2181,6 +2181,52 @@ static int wp_page_copy(struct mm_struct *mm, struct vm_area_struct *vma, 
	return VM_FAULT_OOM;

}



static int wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,

			  unsigned long address, pte_t *page_table,

			  pmd_t *pmd, spinlock_t *ptl, pte_t orig_pte,

			  struct page *old_page)

	__releases(ptl)

{

	int page_mkwrite = 0;



	page_cache_get(old_page);



	/*

	 * Only catch write-faults on shared writable pages,

	 * read-only shared pages can get COWed by

	 * get_user_pages(.write=1, .force=1).

	 */

	if (vma->vm_ops && vma->vm_ops->page_mkwrite) {

		int tmp;



		pte_unmap_unlock(page_table, ptl);

		tmp = do_page_mkwrite(vma, old_page, address);

		if (unlikely(!tmp || (tmp &

				      (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {

			page_cache_release(old_page);

			return tmp;

		}

		/*

		 * Since we dropped the lock we need to revalidate

		 * the PTE as someone else may have changed it.  If

		 * they did, we just return, as we can count on the

		 * MMU to tell us if they didn't also make it writable.

		 */

		page_table = pte_offset_map_lock(mm, pmd, address,

						 &ptl);

		if (!pte_same(*page_table, orig_pte)) {

			unlock_page(old_page);

			pte_unmap_unlock(page_table, ptl);

			page_cache_release(old_page);

			return 0;

		}

		page_mkwrite = 1;

	}



	return wp_page_reuse(mm, vma, address, page_table, ptl,

			     orig_pte, old_page, page_mkwrite, 1);

}



/*

 * This routine handles present pages, when users try to write

 * to a shared page. It is done by copying the page to a new address
@@ -2259,44 +2305,8 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 
		unlock_page(old_page);

	} else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==

					(VM_WRITE|VM_SHARED))) {

		int page_mkwrite = 0;



		page_cache_get(old_page);



		/*

		 * Only catch write-faults on shared writable pages,

		 * read-only shared pages can get COWed by

		 * get_user_pages(.write=1, .force=1).

		 */

		if (vma->vm_ops && vma->vm_ops->page_mkwrite) {

			int tmp;



			pte_unmap_unlock(page_table, ptl);

			tmp = do_page_mkwrite(vma, old_page, address);

			if (unlikely(!tmp || (tmp &

					(VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {

				page_cache_release(old_page);

				return tmp;

			}

			/*

			 * Since we dropped the lock we need to revalidate

			 * the PTE as someone else may have changed it.  If

			 * they did, we just return, as we can count on the

			 * MMU to tell us if they didn't also make it writable.

			 */

			page_table = pte_offset_map_lock(mm, pmd, address,

							 &ptl);

			if (!pte_same(*page_table, orig_pte)) {

				unlock_page(old_page);

				pte_unmap_unlock(page_table, ptl);

				page_cache_release(old_page);

				return 0;

			}

			page_mkwrite = 1;

		}



		return wp_page_reuse(mm, vma, address, page_table, ptl,

				     orig_pte, old_page, page_mkwrite, 1);

		return wp_page_shared(mm, vma, address, page_table, pmd,

				      ptl, orig_pte, old_page);

	}



	/*