uml: activate_mm: remove the dead PF_BORROWED_MM check

use_mm() was changed to use switch_mm() instead of activate_mm(), since
then nobody calls (and nobody should call) activate_mm() with
PF_BORROWED_MM bit set.

As Jeff Dike pointed out, we can also remove the "old != new" check, it is
always true.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/aio.c b/fs/aio.c
index b5253e77eb2f137ee5b1346f848514ad991801e1..0fb3117ddd93d8a517720a744cd415a4b914f63c 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -591,10 +591,6 @@ static void use_mm(struct mm_struct *mm)
        atomic_inc(&mm->mm_count);
        tsk->mm = mm;
        tsk->active_mm = mm;
-       /*
-        * Note that on UML this *requires* PF_BORROWED_MM to be set, otherwise
-        * it won't work. Update it accordingly if you change it here
-        */
        switch_mm(active_mm, mm, tsk);
        task_unlock(tsk);
 

diff --git a/include/asm-um/mmu_context.h b/include/asm-um/mmu_context.h
index 6686fc524ca1aff467688ad52d8976f073a29ea5..54f42e8b0105b7112c9d42a47d41f5fc4fc68312 100644 (file)
--- a/include/asm-um/mmu_context.h
+++ b/include/asm-um/mmu_context.h
@@ -22,16 +22,10 @@ extern void force_flush_all(void);
 static inline void activate_mm(struct mm_struct *old, struct mm_struct *new)
 {
        /*
-        * This is called by fs/exec.c and fs/aio.c. In the first case, for an
-        * exec, we don't need to do anything as we're called from userspace
-        * and thus going to use a new host PID. In the second, we're called
-        * from a kernel thread, and thus need to go doing the mmap's on the
-        * host. Since they're very expensive, we want to avoid that as far as
-        * possible.
+        * This is called by fs/exec.c and sys_unshare()
+        * when the new ->mm is used for the first time.
         */
-       if (old != new && (current->flags & PF_BORROWED_MM))
-               __switch_mm(&new->context.id);
-
+       __switch_mm(&new->context.id);
        arch_dup_mmap(old, new);
 }