Static analysis reported unsigned compare against 0 issue according to
Colin Ian King.

Defined an int temp variable to check the return value of __do_munmap().

Reported-by: Colin Ian King <colin.k...@canonical.com>
Cc: Vlastimil Babka <vba...@suse.cz>
Cc: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Cc: Michal Hocko <mho...@kernel.org>
Cc: Matthew Wilcox <wi...@infradead.org>
Cc: Laurent Dufour <lduf...@linux.vnet.ibm.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Yang Shi <yang....@linux.alibaba.com>
---
Andrew, this should be able to be folded into the original patch.

 mm/mmap.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 68dc4fb..c78f7e9 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -242,17 +242,18 @@ static int do_brk_flags(unsigned long addr, unsigned long 
request, unsigned long
         * __do_munmap() may downgrade mmap_sem to read.
         */
        if (brk <= mm->brk) {
+               int ret;
                /*
                 * mm->brk need to be protected by write mmap_sem, update it
                 * before downgrading mmap_sem.
                 * When __do_munmap fail, it will be restored from origbrk.
                 */
                mm->brk = brk;
-               retval = __do_munmap(mm, newbrk, oldbrk-newbrk, &uf, true);
-               if (retval < 0) {
+               ret = __do_munmap(mm, newbrk, oldbrk-newbrk, &uf, true);
+               if (ret < 0) {
                        mm->brk = origbrk;
                        goto out;
-               } else if (retval == 1)
+               } else if (ret == 1)
                        downgraded = true;
                goto success;
        }
-- 
1.8.3.1

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