[PATCH v4 6/9] mm: Make hugetlb mappings go through mm_get_unmapped_area_vmflags

[Oscar Salvador]

Hugetlb mappings will no longer be special cased but rather go through
the generic mm_get_unmapped_area_vmflags function.
For that to happen, let us remove the .get_unmapped_area from
hugetlbfs_file_operations struct, and hint __get_unmapped_area
that it should not send hugetlb mappings through thp_get_unmapped_area_vmflags
but through mm_get_unmapped_area_vmflags.

Create also a function called hugetlb_mmap_check_and_align() where a
couple of safety checks are being done and the addr is aligned to
the huge page size.
Otherwise we will have to do this in every single function, which
duplicates quite a lot of code.

Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
---
 fs/hugetlbfs/inode.c    | 24 ++++++++++++++++--------
 include/linux/hugetlb.h |  9 ++++-----
 2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 5cf327337e22..2c5f34e315d2 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -258,15 +258,23 @@ generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 			pgoff, flags);
 }
 
-#ifndef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
-static unsigned long
-hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
-			  unsigned long len, unsigned long pgoff,
-			  unsigned long flags)
+unsigned long
+__hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+			    unsigned long len, unsigned long flags)
 {
-	return generic_hugetlb_get_unmapped_area(file, addr, len, pgoff, flags);
+	unsigned long addr0 = 0;
+	struct hstate *h = hstate_file(file);
+
+	if (len & ~huge_page_mask(h))
+		return -EINVAL;
+	if ((flags & MAP_FIXED) && prepare_hugepage_range(file, addr, len))
+		return -EINVAL;
+	if (addr)
+		addr0 = ALIGN(addr, huge_page_size(h));
+
+	return mm_get_unmapped_area_vmflags(current->mm, file, addr, len, pgoff,
+					    flags, 0);
 }
-#endif
 
 /*
  * Someone wants to read @bytes from a HWPOISON hugetlb @page from @offset.
@@ -1300,7 +1308,7 @@ static const struct file_operations hugetlbfs_file_operations = {
 	.read_iter		= hugetlbfs_read_iter,
 	.mmap			= hugetlbfs_file_mmap,
 	.fsync			= noop_fsync,
-	.get_unmapped_area	= hugetlb_get_unmapped_area,
+	.get_unmapped_area	= __hugetlb_get_unmapped_area,
 	.llseek			= default_llseek,
 	.fallocate		= hugetlbfs_fallocate,
 	.fop_flags		= FOP_HUGE_PAGES,
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 368d552e4860..3a81b6126f62 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -546,11 +546,10 @@ static inline struct hstate *hstate_inode(struct inode *i)
 }
 #endif /* !CONFIG_HUGETLBFS */
 
-#ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
-unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
-					unsigned long len, unsigned long pgoff,
-					unsigned long flags);
-#endif /* HAVE_ARCH_HUGETLB_UNMAPPED_AREA */
+unsigned long
+__generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+				    unsigned long len, unsigned long pgoff,
+				    unsigned long flags);
 
 unsigned long
 generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
-- 
2.46.1