Merge branch 'android-4.4-p' of https://android.googlesource.com/kernel/common into lineage-17.1-caf-msm8998

This brings LA.UM.8.4.r1-05300-8x98.0 up to date with
https://android.googlesource.com/kernel/common/ android-4.4-p at commit:
f9991115f0793 Merge 4.4.219 into android-4.4-p

Conflicts:
	drivers/clk/qcom/clk-rcg2.c
	drivers/scsi/sd.c
	drivers/usb/gadget/function/f_fs.c
	drivers/usb/gadget/function/u_serial.c

Change-Id: Ifed3db0ddda828c1697e57e9f73c1b73354bebf7

1 files changed, 22 insertions, 1 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index e7b15518189e..b6ad99903617 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -504,6 +504,15 @@ static inline void get_huge_page_tail(struct page *page)
 
 extern bool __get_page_tail(struct page *page);
 
+static inline int page_ref_count(struct page *page)
+{
+	return atomic_read(&page->_count);
+}
+
+/* 127: arbitrary random number, small enough to assemble well */
+#define page_ref_zero_or_close_to_overflow(page) \
+	((unsigned int) atomic_read(&page->_count) + 127u <= 127u)
+
 static inline void get_page(struct page *page)
 {
 	if (unlikely(PageTail(page)))
@@ -513,10 +522,22 @@ static inline void get_page(struct page *page)
 	 * Getting a normal page or the head of a compound page
 	 * requires to already have an elevated page->_count.
 	 */
-	VM_BUG_ON_PAGE(atomic_read(&page->_count) <= 0, page);
+	VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(page), page);
 	atomic_inc(&page->_count);
 }
 
+static inline __must_check bool try_get_page(struct page *page)
+{
+	if (unlikely(PageTail(page)))
+		if (likely(__get_page_tail(page)))
+			return true;
+
+	if (WARN_ON_ONCE(atomic_read(&page->_count) <= 0))
+		return false;
+	atomic_inc(&page->_count);
+	return true;
+}
+
 static inline struct page *virt_to_head_page(const void *x)
 {
 	struct page *page = virt_to_page(x);