1 files changed, 9 insertions, 2 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 96fa79fb6ad3..5808fadd3944 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -83,6 +83,7 @@ enum sgp_type {
         SGP_READ,       /* don't exceed i_size, don't allocate page */
         SGP_CACHE,      /* don't exceed i_size, may allocate page */
         SGP_WRITE,      /* may exceed i_size, may allocate page */
+        SGP_NOPAGE,     /* same as SGP_CACHE, return with page locked */
 };
 
 static int shmem_getpage(struct inode *inode, unsigned long idx,
@@ -1289,8 +1290,10 @@ repeat:
         }
 done:
         if (*pagep != filepage) {
-                unlock_page(filepage);
                 *pagep = filepage;
+                if (sgp != SGP_NOPAGE)
+                        unlock_page(filepage);
+
         }
         return 0;
 
@@ -1310,13 +1313,15 @@ static struct page *shmem_nopage(struct vm_area_struct *vma,
         unsigned long idx;
         int error;
 
+        BUG_ON(!(vma->vm_flags & VM_CAN_INVALIDATE));
+
         idx = (address - vma->vm_start) >> PAGE_SHIFT;
         idx += vma->vm_pgoff;
         idx >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
         if (((loff_t) idx << PAGE_CACHE_SHIFT) >= i_size_read(inode))
                 return NOPAGE_SIGBUS;
 
-        error = shmem_getpage(inode, idx, &page, SGP_CACHE, type);
+        error = shmem_getpage(inode, idx, &page, SGP_NOPAGE, type);
         if (error)
                 return (error == -ENOMEM)? NOPAGE_OOM: NOPAGE_SIGBUS;
 
@@ -1414,6 +1419,7 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
 {
         file_accessed(file);
         vma->vm_ops = &shmem_vm_ops;
+        vma->vm_flags |= VM_CAN_INVALIDATE;
         return 0;
 }
 
@@ -2596,5 +2602,6 @@ int shmem_zero_setup(struct vm_area_struct *vma)
                 fput(vma->vm_file);
         vma->vm_file = file;
         vma->vm_ops = &shmem_vm_ops;
+        vma->vm_flags |= VM_CAN_INVALIDATE;
         return 0;
 }