mmap: allow MAP_HUGETLB for hugetlbfs files v2

It is counterintuitive at best that mmap'ing a hugetlbfs file with
MAP_HUGETLB fails, while mmap'ing it without will a) succeed and b)
return huge pages.

v2: use is_file_hugepages(), as suggested by Jianguo

Signed-off-by: Joern Engel <joern@logfs.org>
Cc: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index 8468ffd05bae..0718c175db8f 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1358,13 +1358,14 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 
         if (!(flags & MAP_ANONYMOUS)) {
                 audit_mmap_fd(fd, flags);
-                if (unlikely(flags & MAP_HUGETLB))
-                        return -EINVAL;
                 file = fget(fd);
                 if (!file)
                         goto out;
                 if (is_file_hugepages(file))
                         len = ALIGN(len, huge_page_size(hstate_file(file)));
+                retval = -EINVAL;
+                if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
+                        goto out_fput;
         } else if (flags & MAP_HUGETLB) {
                 struct user_struct *user = NULL;
                 struct hstate *hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) &
@@ -1391,6 +1392,7 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
         flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
 
         retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
+out_fput:
         if (file)
                 fput(file);
 out: