mremap: simplify the "overlap" check in mremap_to()

Minor, but this check is overcomplicated.  Two half-intervals do NOT
overlap if END1 <= START2 || END2 <= START1, mremap_to() just needs to
negate this check.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mremap.c b/mm/mremap.c
index d3f42be..5a71cce 100644 (file)
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -407,13 +407,8 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
        if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
                goto out;
 
-       /* Check if the location we're moving into overlaps the
-        * old location at all, and fail if it does.
-        */
-       if ((new_addr <= addr) && (new_addr+new_len) > addr)
-               goto out;
-
-       if ((addr <= new_addr) && (addr+old_len) > new_addr)
+       /* Ensure the old/new locations do not overlap */
+       if (addr + old_len > new_addr && new_addr + new_len > addr)
                goto out;
 
        ret = do_munmap(mm, new_addr, new_len);