1 files changed, 110 insertions, 0 deletions
diff --git a/mm/msync.c b/mm/msync.c
new file mode 100644
index 000000000..69c6d2029
--- /dev/null
+++ b/mm/msync.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *	linux/mm/msync.c
+ *
+ * Copyright (C) 1994-1999  Linus Torvalds
+ */
+
+/*
+ * The msync() system call.
+ */
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/file.h>
+#include <linux/syscalls.h>
+#include <linux/sched.h>
+
+/*
+ * MS_SYNC syncs the entire file - including mappings.
+ *
+ * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
+ * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
+ * Now it doesn't do anything, since dirty pages are properly tracked.
+ *
+ * The application may now run fsync() to
+ * write out the dirty pages and wait on the writeout and check the result.
+ * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
+ * async writeout immediately.
+ * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to
+ * applications.
+ */
+SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
+{
+	unsigned long end;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	int unmapped_error = 0;
+	int error = -EINVAL;
+
+	start = untagged_addr(start);
+
+	if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
+		goto out;
+	if (offset_in_page(start))
+		goto out;
+	if ((flags & MS_ASYNC) && (flags & MS_SYNC))
+		goto out;
+	error = -ENOMEM;
+	len = (len + ~PAGE_MASK) & PAGE_MASK;
+	end = start + len;
+	if (end < start)
+		goto out;
+	error = 0;
+	if (end == start)
+		goto out;
+	/*
+	 * If the interval [start,end) covers some unmapped address ranges,
+	 * just ignore them, but return -ENOMEM at the end.
+	 */
+	mmap_read_lock(mm);
+	vma = find_vma(mm, start);
+	for (;;) {
+		struct file *file;
+		loff_t fstart, fend;
+
+		/* Still start < end. */
+		error = -ENOMEM;
+		if (!vma)
+			goto out_unlock;
+		/* Here start < vma->vm_end. */
+		if (start < vma->vm_start) {
+			start = vma->vm_start;
+			if (start >= end)
+				goto out_unlock;
+			unmapped_error = -ENOMEM;
+		}
+		/* Here vma->vm_start <= start < vma->vm_end. */
+		if ((flags & MS_INVALIDATE) &&
+				(vma->vm_flags & VM_LOCKED)) {
+			error = -EBUSY;
+			goto out_unlock;
+		}
+		file = vma->vm_file;
+		fstart = (start - vma->vm_start) +
+			 ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
+		fend = fstart + (min(end, vma->vm_end) - start) - 1;
+		start = vma->vm_end;
+		if ((flags & MS_SYNC) && file &&
+				(vma->vm_flags & VM_SHARED)) {
+			get_file(file);
+			mmap_read_unlock(mm);
+			error = vfs_fsync_range(file, fstart, fend, 1);
+			fput(file);
+			if (error || start >= end)
+				goto out;
+			mmap_read_lock(mm);
+			vma = find_vma(mm, start);
+		} else {
+			if (start >= end) {
+				error = 0;
+				goto out_unlock;
+			}
+			vma = vma->vm_next;
+		}
+	}
+out_unlock:
+	mmap_read_unlock(mm);
+out:
+	return error ? : unmapped_error;
+}