ksm: remove dedicated macro KSM_FLAG_MASK

The macro KSM_FLAG_MASK is used in rmap_walk_ksm() only.  So we can
replace ~KSM_FLAG_MASK with PAGE_MASK to remove this dedicated macro and
make code more consistent because PAGE_MASK is used elsewhere in this
file.

Link: https://lkml.kernel.org/r/20210330140228.45635-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/ksm.c

@@ -215,8 +215,6 @@ struct rmap_item {
 #define SEQNR_MASK	0x0ff	/* low bits of unstable tree seqnr */
 #define UNSTABLE_FLAG	0x100	/* is a node of the unstable tree */
 #define STABLE_FLAG	0x200	/* is listed from the stable tree */
-#define KSM_FLAG_MASK	(SEQNR_MASK|UNSTABLE_FLAG|STABLE_FLAG)
-				/* to mask all the flags */
 
 /* The stable and unstable tree heads */
 static struct rb_root one_stable_tree[1] = { RB_ROOT };
@@ -2631,7 +2629,7 @@ again:
 			vma = vmac->vma;
 
 			/* Ignore the stable/unstable/sqnr flags */
-			addr = rmap_item->address & ~KSM_FLAG_MASK;
+			addr = rmap_item->address & PAGE_MASK;
 
 			if (addr < vma->vm_start || addr >= vma->vm_end)
 				continue;