[PATCH v2 4/4] mm: Refactor do_wp_page handling of shared vma into a function

[Shachar Raindel <raindel@mellanox.com>]

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: Shachar Raindel <raindel@mellanox.com>
---
 mm/memory.c | 86 ++++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 48 insertions(+), 38 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index c7c0df2..e730628 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2227,6 +2227,52 @@ oom:
 	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;
+	int ret;
+
+	/*
+	 * 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)
+		goto no_mkwrite;
+
+	page_cache_get(old_page);
+	pte_unmap_unlock(page_table, ptl);
+	ret = do_page_mkwrite(vma, old_page, address);
+	if (unlikely(!ret || (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
+		page_cache_release(old_page);
+		return ret;
+	}
+	/*
+	 * 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;
+
+no_mkwrite:
+	get_page(old_page);
+
+	return wp_page_reuse(mm, vma, address, page_table, ptl, orig_pte,
+			     old_page, 1, page_mkwrite);
+}
+
 /*
  * 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
@@ -2305,44 +2351,8 @@ 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;
-
-		/*
-		 * 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;
-			page_cache_get(old_page);
-			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;
-		}
-		get_page(old_page);
-
-		return wp_page_reuse(mm, vma, address, page_table, ptl,
-				     orig_pte, old_page, 1, page_mkwrite);
+		return wp_page_shared(mm, vma, address, page_table, pmd,
+				      ptl, orig_pte, old_page);
 	}
 
 	/*
-- 
1.7.11.2

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>