1 files changed, 9 insertions, 2 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 96fa79f..5808fad 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;
 }