sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h>

We are going to split <linux/sched/task.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/task.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 2df6d36..a397057 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -74,6 +74,7 @@
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/sched/signal.h>
+#include <linux/sched/task.h>
 #include <linux/jiffies.h>
 #include <linux/delay.h>
 #include <linux/export.h>
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b74984d..27f7210 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -41,6 +41,7 @@
 #include <linux/page-flags.h>
 #include <linux/kernel-page-flags.h>
 #include <linux/sched/signal.h>
+#include <linux/sched/task.h>
 #include <linux/ksm.h>
 #include <linux/rmap.h>
 #include <linux/export.h>
diff --git a/mm/memory.c b/mm/memory.c
index d4994a2..a97a4ce 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -43,6 +43,7 @@
 #include <linux/sched/mm.h>
 #include <linux/sched/coredump.h>
 #include <linux/sched/numa_balancing.h>
+#include <linux/sched/task.h>
 #include <linux/hugetlb.h>
 #include <linux/mman.h>
 #include <linux/swap.h>
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 69f75b0..d083714 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -24,6 +24,7 @@
 #include <linux/sched.h>
 #include <linux/sched/mm.h>
 #include <linux/sched/coredump.h>
+#include <linux/sched/task.h>
 #include <linux/swap.h>
 #include <linux/timex.h>
 #include <linux/jiffies.h>
diff --git a/mm/rmap.c b/mm/rmap.c
index 0367a05..2da487d 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -47,6 +47,7 @@
 
 #include <linux/mm.h>
 #include <linux/sched/mm.h>
+#include <linux/sched/task.h>
 #include <linux/pagemap.h>
 #include <linux/swap.h>
 #include <linux/swapops.h>
diff --git a/mm/swapfile.c b/mm/swapfile.c
index ff2bf3f..521ef9b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -7,6 +7,7 @@
 
 #include <linux/mm.h>
 #include <linux/sched/mm.h>
+#include <linux/sched/task.h>
 #include <linux/hugetlb.h>
 #include <linux/mman.h>
 #include <linux/slab.h>
diff --git a/mm/usercopy.c b/mm/usercopy.c
index 7ccad05..d155e12 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -17,6 +17,8 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
+#include <linux/sched/task.h>
+#include <linux/sched/task_stack.h>
 #include <asm/sections.h>
 
 enum {