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@xxxxxxxxxxxx>
Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Acked-by: Haggai Eran <haggaie@xxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Peter Feiner <pfeiner@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
---
mm/memory.c | 85 ++++++++++++++++++++++++++++++++++---------------------------
1 file changed, 47 insertions(+), 38 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index b9e951c..b2f1dc1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2214,6 +2214,51 @@ 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
@@ -2292,44 +2337,8 @@ 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
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