[PATCH] mmap: allow MAP_HUGETLB for hugetlbfs files v2

["Jörn Engel" <joern@logfs.org>]

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>
---
 mm/mmap.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 2a594246..cdc8e7a 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1322,11 +1322,12 @@ 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;
+		retval = -EINVAL;
+		if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
+			goto out_fput;
 	} else if (flags & MAP_HUGETLB) {
 		struct user_struct *user = NULL;
 		/*
@@ -1346,6 +1347,7 @@ 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:
-- 
1.7.10.4

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