From: Piotr Kwapulinski <kwapulinski.piotr@gmail.com>
Date: Wed, 24 Jun 2015 23:58:39 +0000 (-0700)
Subject: mm/mmap.c: optimization of do_mmap_pgoff function
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=e37609bb36f706c954e82e580e2e790e9d5caef8;p=openwrt%2Fstaging%2Fblogic.git

mm/mmap.c: optimization of do_mmap_pgoff function

The simple check for zero length memory mapping may be performed
earlier.  So that in case of zero length memory mapping some unnecessary
code is not executed at all.  It does not make the code less readable
and saves some CPU cycles.

Signed-off-by: Piotr Kwapulinski <kwapulinski.piotr@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/mmap.c b/mm/mmap.c
index bb50cacc3ea5..aa632ade2be7 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1258,6 +1258,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
 
 	*populate = 0;
 
+	if (!len)
+		return -EINVAL;
+
 	/*
 	 * Does the application expect PROT_READ to imply PROT_EXEC?
 	 *
@@ -1268,9 +1271,6 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
 		if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
 			prot |= PROT_EXEC;
 
-	if (!len)
-		return -EINVAL;
-
 	if (!(flags & MAP_FIXED))
 		addr = round_hint_to_min(addr);