mm/mmap: optimize a branch judgment in ksys_mmap_pgoff()

Look at the pseudo code below.  It's very clear that, the judgement
"!is_file_hugepages(file)" at 3) is duplicated to the one at 1), we can
use "else if" to avoid it.  And the assignment "retval = -EINVAL" at 2) is
only needed by the branch 3), because "retval" will be overwritten at 4).

No functional change, but it can reduce the code size. Maybe more clearer?
Before:
text    data     bss     dec     hex filename
28733    1590       1   30324    7674 mm/mmap.o

After:
text    data     bss     dec     hex filename
28701    1590       1   30292    7654 mm/mmap.o

====pseudo code====:
	if (!(flags & MAP_ANONYMOUS)) {
		...
1)		if (is_file_hugepages(file))
			len = ALIGN(len, huge_page_size(hstate_file(file)));
2)		retval = -EINVAL;
3)		if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
			goto out_fput;
	} else if (flags & MAP_HUGETLB) {
		...
	}
	...

4)	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
out_fput:
	...
	return retval;

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200705080112.1405-1-thunder.leizhen@huawei.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index dcdab26..853ae3a 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1562,11 +1562,12 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
                file = fget(fd);
                if (!file)
                        return -EBADF;
-               if (is_file_hugepages(file))
+               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)))
+               } else if (unlikely(flags & MAP_HUGETLB)) {
+                       retval = -EINVAL;
                        goto out_fput;
+               }
        } else if (flags & MAP_HUGETLB) {
                struct user_struct *user = NULL;
                struct hstate *hs;