[RFC V2 16/37] dmemfs: introduce ->split() to dmemfs_vm_ops

[yulei . kernel]

From: Yulei Zhang <yuleixzhang@xxxxxxxxxxx>

It is required by __split_vma() to adjust vma. munmap() which create
hole unaligned to pagesize in dmemfs-mapping should be forbidden.

Signed-off-by: Chen Zhuo <sagazchen@xxxxxxxxxxx>
Signed-off-by: Yulei Zhang <yuleixzhang@xxxxxxxxxxx>
---
 fs/dmemfs/inode.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/dmemfs/inode.c b/fs/dmemfs/inode.c
index 443f2e1..ab6a492 100644
--- a/fs/dmemfs/inode.c
+++ b/fs/dmemfs/inode.c
@@ -450,6 +450,13 @@ static bool check_vma_access(struct vm_area_struct *vma, int write)
 	return len;
 }
 
+static int dmemfs_split(struct vm_area_struct *vma, unsigned long addr)
+{
+	if (addr & (dmem_page_size(file_inode(vma->vm_file)) - 1))
+		return -EINVAL;
+	return 0;
+}
+
 static vm_fault_t dmemfs_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
@@ -484,6 +491,7 @@ static unsigned long dmemfs_pagesize(struct vm_area_struct *vma)
 }
 
 static const struct vm_operations_struct dmemfs_vm_ops = {
+	.split = dmemfs_split,
 	.fault = dmemfs_fault,
 	.pagesize = dmemfs_pagesize,
 	.access = dmemfs_access_dmem,
-- 
1.8.3.1