linux-kernel - [PATCH v3 19/22] mm/mshare: Add an ioctl for unmapping objects in an mshare region

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Message-ID: <20250820010415.699353-20-anthony.yznaga@oracle.com>
Date: Tue, 19 Aug 2025 18:04:12 -0700
From: Anthony Yznaga <anthony.yznaga@...cle.com>
To: linux-mm@...ck.org
Cc: akpm@...ux-foundation.org, andreyknvl@...il.com, arnd@...db.de,
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Subject: [PATCH v3 19/22] mm/mshare: Add an ioctl for unmapping objects in an mshare region

The arguments are the same as munmap() except that the start of the
mapping is specified as an offset into the mshare region instead of
as an address.

Signed-off-by: Anthony Yznaga <anthony.yznaga@...cle.com>
---
 include/uapi/linux/msharefs.h |  7 +++++++
 mm/mshare.c                   | 37 +++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/include/uapi/linux/msharefs.h b/include/uapi/linux/msharefs.h
index ad129beeef62..fb0235d1e384 100644
--- a/include/uapi/linux/msharefs.h
+++ b/include/uapi/linux/msharefs.h
@@ -19,6 +19,7 @@
  * msharefs specific ioctl commands
  */
 #define MSHAREFS_CREATE_MAPPING	_IOW('x', 0,  struct mshare_create)
+#define MSHAREFS_UNMAP		_IOW('x', 1,  struct mshare_unmap)
 
 struct mshare_create {
 	__u64 region_offset;
@@ -28,4 +29,10 @@ struct mshare_create {
 	__u32 flags;
 	__u32 fd;
 };
+
+struct mshare_unmap {
+	__u64 region_offset;
+	__u64 size;
+};
+
 #endif
diff --git a/mm/mshare.c b/mm/mshare.c
index ebec51e655e4..b1e02f5e1f60 100644
--- a/mm/mshare.c
+++ b/mm/mshare.c
@@ -394,11 +394,41 @@ msharefs_create_mapping(struct mshare_data *m_data, struct mshare_create *mcreat
 	return error;
 }
 
+static long
+msharefs_unmap(struct mshare_data *m_data, struct mshare_unmap *munmap)
+{
+	struct mm_struct *host_mm = m_data->mm;
+	unsigned long mshare_start, mshare_end, mshare_size;
+	unsigned long region_offset = munmap->region_offset;
+	unsigned long size = munmap->size;
+	unsigned long addr;
+	int error;
+
+	mshare_start = m_data->start;
+	mshare_size = m_data->size;
+	mshare_end = mshare_start + mshare_size;
+	addr = mshare_start + region_offset;
+
+	if ((size > mshare_size) || (region_offset >= mshare_size) ||
+	    (addr + size > mshare_end))
+		return -EINVAL;
+
+	if (mmap_write_lock_killable(host_mm))
+		return -EINTR;
+
+	error = do_munmap(host_mm, addr, size, NULL);
+
+	mmap_write_unlock(host_mm);
+
+	return error;
+}
+
 static long
 msharefs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct mshare_data *m_data = filp->private_data;
 	struct mshare_create mcreate;
+	struct mshare_unmap munmap;
 
 	if (!mshare_is_initialized(m_data))
 		return -EINVAL;
@@ -411,6 +441,13 @@ msharefs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 
 		return msharefs_create_mapping(m_data, &mcreate);
 
+	case MSHAREFS_UNMAP:
+		if (copy_from_user(&munmap, (struct mshare_unmap __user *)arg,
+			sizeof(munmap)))
+			return -EFAULT;
+
+		return msharefs_unmap(m_data, &munmap);
+
 	default:
 		return -ENOTTY;
 	}
-- 
2.47.1