[PATCH 01/10] mm/huge_memory: rename freeze_page() to unmap_page()

[PATCH 01/10] mm/huge_memory: rename freeze_page() to unmap_page()

[Hugh Dickins]

The term "freeze" is used in several ways in the kernel, and in mm it
has the particular meaning of forcing page refcount temporarily to 0.
freeze_page() is just too confusing a name for a function that unmaps
a page: rename it unmap_page(), and rename unfreeze_page() remap_page().

Went to change the mention of freeze_page() added later in mm/rmap.c,
but found it to be incorrect: ordinary page reclaim reaches there too;
but the substance of the comment still seems correct, so edit it down.

Fixes: e9b61f19858a5 ("thp: reintroduce split_huge_page()")
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: stable@vger.kernel.org # 4.8+
---
 mm/huge_memory.c | 12 ++++++------
 mm/rmap.c        | 13 +++----------
 2 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 55478ab3c83b..30100fac2341 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2350,7 +2350,7 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma,
 	}
 }
 
-static void freeze_page(struct page *page)
+static void unmap_page(struct page *page)
 {
 	enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
 		TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
@@ -2365,7 +2365,7 @@ static void freeze_page(struct page *page)
 	VM_BUG_ON_PAGE(!unmap_success, page);
 }
 
-static void unfreeze_page(struct page *page)
+static void remap_page(struct page *page)
 {
 	int i;
 	if (PageTransHuge(page)) {
@@ -2483,7 +2483,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 
 	spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
 
-	unfreeze_page(head);
+	remap_page(head);
 
 	for (i = 0; i < HPAGE_PMD_NR; i++) {
 		struct page *subpage = head + i;
@@ -2664,7 +2664,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
 	}
 
 	/*
-	 * Racy check if we can split the page, before freeze_page() will
+	 * Racy check if we can split the page, before unmap_page() will
 	 * split PMDs
 	 */
 	if (!can_split_huge_page(head, &extra_pins)) {
@@ -2673,7 +2673,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
 	}
 
 	mlocked = PageMlocked(page);
-	freeze_page(head);
+	unmap_page(head);
 	VM_BUG_ON_PAGE(compound_mapcount(head), head);
 
 	/* Make sure the page is not on per-CPU pagevec as it takes pin */
@@ -2727,7 +2727,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
 fail:		if (mapping)
 			xa_unlock(&mapping->i_pages);
 		spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
-		unfreeze_page(head);
+		remap_page(head);
 		ret = -EBUSY;
 	}
 
diff --git a/mm/rmap.c b/mm/rmap.c
index 1e79fac3186b..85b7f9423352 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1627,16 +1627,9 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 						      address + PAGE_SIZE);
 		} else {
 			/*
-			 * We should not need to notify here as we reach this
-			 * case only from freeze_page() itself only call from
-			 * split_huge_page_to_list() so everything below must
-			 * be true:
-			 *   - page is not anonymous
-			 *   - page is locked
-			 *
-			 * So as it is a locked file back page thus it can not
-			 * be remove from the page cache and replace by a new
-			 * page before mmu_notifier_invalidate_range_end so no
+			 * This is a locked file-backed page, thus it cannot
+			 * be removed from the page cache and replaced by a new
+			 * page before mmu_notifier_invalidate_range_end, so no
 			 * concurrent thread might update its page table to
 			 * point at new page while a device still is using this
 			 * page.
-- 
2.20.0.rc0.387.gc7a69e6b6c-goog

Re: [PATCH 01/10] mm/huge_memory: rename freeze_page() to unmap_page()

[Kirill A. Shutemov]

On Mon, Nov 26, 2018 at 03:16:28PM -0800, Hugh Dickins wrote:
> The term "freeze" is used in several ways in the kernel, and in mm it
> has the particular meaning of forcing page refcount temporarily to 0.
> freeze_page() is just too confusing a name for a function that unmaps
> a page: rename it unmap_page(), and rename unfreeze_page() remap_page().
> 
> Went to change the mention of freeze_page() added later in mm/rmap.c,
> but found it to be incorrect: ordinary page reclaim reaches there too;
> but the substance of the comment still seems correct, so edit it down.
> 
> Fixes: e9b61f19858a5 ("thp: reintroduce split_huge_page()")
> Signed-off-by: Hugh Dickins <hughd@google.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Jerome Glisse <jglisse@redhat.com>
> Cc: stable@vger.kernel.org # 4.8+

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

-- 
 Kirill A. Shutemov