[PATCH 17/20] mshare: add MSHAREFS_UNMAP

[Anthony Yznaga <anthony.yznaga@oracle.com>]

Add an ioctl for unmapping objects in an mshare region.

Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
---
 include/uapi/linux/msharefs.h |  7 ++++++
 mm/mshare.c                   | 44 +++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/include/uapi/linux/msharefs.h b/include/uapi/linux/msharefs.h
index fea0afdf000d..f7af1f2b5ee7 100644
--- a/include/uapi/linux/msharefs.h
+++ b/include/uapi/linux/msharefs.h
@@ -21,6 +21,7 @@
 #define MSHAREFS_GET_SIZE	_IOR('x', 0,  struct mshare_info)
 #define MSHAREFS_SET_SIZE	_IOW('x', 1,  struct mshare_info)
 #define MSHAREFS_CREATE_MAPPING	_IOW('x', 2,  struct mshare_create)
+#define MSHAREFS_UNMAP		_IOW('x', 3,  struct mshare_unmap)
 
 struct mshare_info {
 	__u64 start;
@@ -35,4 +36,10 @@ struct mshare_create {
 	__u32 flags;
 	__u32 fd;
 };
+
+struct mshare_unmap {
+	__u64 addr;
+	__u64 size;
+};
+
 #endif
diff --git a/mm/mshare.c b/mm/mshare.c
index d70f10210b46..8f53b8132895 100644
--- a/mm/mshare.c
+++ b/mm/mshare.c
@@ -241,6 +241,32 @@ msharefs_create_mapping(struct mm_struct *host_mm, struct mshare_data *m_data,
 	return err;
 }
 
+static long
+msharefs_unmap(struct mm_struct *host_mm, struct mshare_data *m_data,
+		  struct mshare_unmap *m_unmap)
+{
+	unsigned long mshare_start, mshare_end;
+	unsigned long addr = m_unmap->addr;
+	unsigned long size = m_unmap->size;
+	int err;
+
+	mshare_start = m_data->minfo.start;
+	mshare_end = mshare_start + m_data->minfo.size;
+
+	if ((addr < mshare_start) || (addr >= mshare_end) ||
+	    (addr + size > mshare_end))
+		return -EINVAL;
+
+	if (mmap_write_lock_killable(host_mm))
+		return -EINTR;
+
+	err = do_munmap(host_mm, addr, size, NULL);
+
+	mmap_write_unlock(host_mm);
+
+	return err;
+}
+
 static long
 msharefs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
@@ -248,6 +274,7 @@ msharefs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	struct mm_struct *host_mm = m_data->mm;
 	struct mshare_info minfo;
 	struct mshare_create mcreate;
+	struct mshare_unmap m_unmap;
 
 	switch (cmd) {
 	case MSHAREFS_GET_SIZE:
@@ -293,6 +320,23 @@ msharefs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 
 		return msharefs_create_mapping(host_mm, m_data, &mcreate);
 
+	case MSHAREFS_UNMAP:
+		if (copy_from_user(&m_unmap, (struct mshare_unmap __user *)arg,
+			sizeof(m_unmap)))
+			return -EFAULT;
+
+		/*
+		 * validate mshare region
+		 */
+		spin_lock(&m_data->m_lock);
+		if (m_data->minfo.size == 0) {
+			spin_unlock(&m_data->m_lock);
+			return -EINVAL;
+		}
+		spin_unlock(&m_data->m_lock);
+
+		return msharefs_unmap(host_mm, m_data, &m_unmap);
+
 	default:
 		return -ENOTTY;
 	}
-- 
2.43.5