[PATCH 2/3] mm, thp: make mapping address of libraries THP align

[Rongwei Wang <rongwei.wang@linux.alibaba.com>]

For shared libraries, ld.so seems not to consider p_align well, as shown
below.
$ readelf -l /usr/lib64/libc-2.17.so
LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
               0x00000000001c2fe8 0x00000000001c2fe8  R E    200000
$ cat /proc/1/smaps
7fecc4072000-7fecc4235000 r-xp 00000000 08:03 655802  /usr/lib64/libc-2.17.so

This makes the mapping address allocated by 'get_unmapped_area'
align with 2M for libraries, to facilitate file THP for .text
section as far as possible.

Signed-off-by: Gang Deng <gavin.dg@linux.alibaba.com>
Signed-off-by: Xu Yu <xuyu@linux.alibaba.com>
Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com>
---
 include/linux/huge_mm.h | 12 ++++++++++++
 mm/huge_memory.c        | 15 +++++++++++++++
 mm/mmap.c               | 18 ++++++++++++++++++
 3 files changed, 45 insertions(+)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 95b718031ef3..ddbc0d19f90f 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -147,8 +147,20 @@ static inline bool transhuge_vma_enabled(struct vm_area_struct *vma,
 #define hugetext_enabled()			\
 	(transparent_hugepage_flags &		\
 	 (1<<TRANSPARENT_HUGEPAGE_HUGETEXT_ENABLED_FLAG))
+
+extern unsigned long hugetext_get_unmapped_area(struct file *filp,
+		unsigned long addr, unsigned long len, unsigned long pgoff,
+		unsigned long flags);
 #else
 #define hugetext_enabled()	false
+
+static inline unsigned long hugetext_get_unmapped_area(struct file *filp,
+		unsigned long addr, unsigned long len, unsigned long pgoff,
+		unsigned long flags)
+{
+	BUILD_BUG();
+	return 0;
+}
 #endif /* CONFIG_HUGETEXT */
 
 static inline bool vma_is_hugetext(struct vm_area_struct *vma,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f6fffb5c5130..076a74cdc214 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -650,6 +650,21 @@ unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 }
 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 
+#ifdef CONFIG_HUGETEXT
+unsigned long hugetext_get_unmapped_area(struct file *filp, unsigned long addr,
+		unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+	unsigned long ret;
+	loff_t off = (loff_t)pgoff << PAGE_SHIFT;
+
+	ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
+	if (ret)
+		return ret;
+
+	return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
+}
+#endif /* CONFIG_HUGETEXT */
+
 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 			struct page *page, gfp_t gfp)
 {
diff --git a/mm/mmap.c b/mm/mmap.c
index 88dcc5c25225..cad94a13edc2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2242,8 +2242,26 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
 
 	get_area = current->mm->get_unmapped_area;
 	if (file) {
+#ifdef CONFIG_HUGETEXT
+		/*
+		 * Prior to the file->f_op->get_unmapped_area.
+		 *
+		 * If hugetext is enabled, except for MAP_FIXED, it always
+		 * make the mapping address of files that have executable
+		 * attribute be mapped in 2MB alignment.
+		 */
+		struct inode *inode = file_inode(file);
+
+		if (hugetext_enabled() && (inode->i_mode & 0111) &&
+				(!file->f_op->get_unmapped_area ||
+				 file->f_op->get_unmapped_area == thp_get_unmapped_area))
+			get_area = hugetext_get_unmapped_area;
+		else if (file->f_op->get_unmapped_area)
+			get_area = file->f_op->get_unmapped_area;
+#else
 		if (file->f_op->get_unmapped_area)
 			get_area = file->f_op->get_unmapped_area;
+#endif
 	} else if (flags & MAP_SHARED) {
 		/*
 		 * mmap_region() will call shmem_zero_setup() to create a file,
-- 
2.27.0