uprobes: __replace_page() needs munlock_vma_page()

Like do_wp_page(), __replace_page() should do munlock_vma_page()
for the case when the old page still has other !VM_LOCKED
mappings. Unfortunately this needs mm/internal.h.

Also, move put_page() outside of ptl lock. This doesn't really
matter but looks a bit better.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182249.GA20372@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index bb30a4fc5050..c08a22d02f72 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -32,6 +32,7 @@
 #include <linux/swap.h>         /* try_to_free_swap */
 #include <linux/ptrace.h>       /* user_enable_single_step */
 #include <linux/kdebug.h>       /* notifier mechanism */
+#include "../../mm/internal.h"  /* munlock_vma_page */
 
 #include <linux/uprobes.h>
 
@@ -141,7 +142,7 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
         pte_t *ptep;
         int err;
 
-        /* freeze PageSwapCache() for try_to_free_swap() below */
+        /* For try_to_free_swap() and munlock_vma_page() below */
         lock_page(page);
 
         err = -EAGAIN;
@@ -164,9 +165,12 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
         page_remove_rmap(page);
         if (!page_mapped(page))
                 try_to_free_swap(page);
-        put_page(page);
         pte_unmap_unlock(ptep, ptl);
 
+        if (vma->vm_flags & VM_LOCKED)
+                munlock_vma_page(page);
+        put_page(page);
+
         err = 0;
  unlock:
         unlock_page(page);