Fixed MTP to work with TWRP

fs/ncpfs/mmap.c

@@ -0,0 +1,127 @@
+/*
+ *  mmap.c
+ *
+ *  Copyright (C) 1995, 1996 by Volker Lendecke
+ *  Modified 1997 Peter Waltenberg, Bill Hawes, David Woodhouse for 2.1 dcache
+ *
+ */
+
+#include <linux/stat.h>
+#include <linux/time.h>
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/shm.h>
+#include <linux/errno.h>
+#include <linux/mman.h>
+#include <linux/string.h>
+#include <linux/fcntl.h>
+#include <linux/memcontrol.h>
+
+#include <asm/uaccess.h>
+
+#include "ncp_fs.h"
+
+/*
+ * Fill in the supplied page for mmap
+ * XXX: how are we excluding truncate/invalidate here? Maybe need to lock
+ * page?
+ */
+static int ncp_file_mmap_fault(struct vm_area_struct *area,
+					struct vm_fault *vmf)
+{
+	struct file *file = area->vm_file;
+	struct dentry *dentry = file->f_path.dentry;
+	struct inode *inode = dentry->d_inode;
+	char *pg_addr;
+	unsigned int already_read;
+	unsigned int count;
+	int bufsize;
+	int pos; /* XXX: loff_t ? */
+
+	/*
+	 * ncpfs has nothing against high pages as long
+	 * as recvmsg and memset works on it
+	 */
+	vmf->page = alloc_page(GFP_HIGHUSER);
+	if (!vmf->page)
+		return VM_FAULT_OOM;
+	pg_addr = kmap(vmf->page);
+	pos = vmf->pgoff << PAGE_SHIFT;
+
+	count = PAGE_SIZE;
+	/* what we can read in one go */
+	bufsize = NCP_SERVER(inode)->buffer_size;
+
+	already_read = 0;
+	if (ncp_make_open(inode, O_RDONLY) >= 0) {
+		while (already_read < count) {
+			int read_this_time;
+			int to_read;
+
+			to_read = bufsize - (pos % bufsize);
+
+			to_read = min_t(unsigned int, to_read, count - already_read);
+
+			if (ncp_read_kernel(NCP_SERVER(inode),
+				     NCP_FINFO(inode)->file_handle,
+				     pos, to_read,
+				     pg_addr + already_read,
+				     &read_this_time) != 0) {
+				read_this_time = 0;
+			}
+			pos += read_this_time;
+			already_read += read_this_time;
+
+			if (read_this_time < to_read) {
+				break;
+			}
+		}
+		ncp_inode_close(inode);
+
+	}
+
+	if (already_read < PAGE_SIZE)
+		memset(pg_addr + already_read, 0, PAGE_SIZE - already_read);
+	flush_dcache_page(vmf->page);
+	kunmap(vmf->page);
+
+	/*
+	 * If I understand ncp_read_kernel() properly, the above always
+	 * fetches from the network, here the analogue of disk.
+	 * -- nyc
+	 */
+	count_vm_event(PGMAJFAULT);
+	mem_cgroup_count_vm_event(area->vm_mm, PGMAJFAULT);
+	return VM_FAULT_MAJOR;
+}
+
+static const struct vm_operations_struct ncp_file_mmap =
+{
+	.fault = ncp_file_mmap_fault,
+};
+
+
+/* This is used for a general mmap of a ncp file */
+int ncp_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct inode *inode = file_inode(file);
+	
+	ncp_dbg(1, "called\n");
+
+	if (!ncp_conn_valid(NCP_SERVER(inode)))
+		return -EIO;
+
+	/* only PAGE_COW or read-only supported now */
+	if (vma->vm_flags & VM_SHARED)
+		return -EINVAL;
+	/* we do not support files bigger than 4GB... We eventually 
+	   supports just 4GB... */
+	if (vma_pages(vma) + vma->vm_pgoff
+	   > (1U << (32 - PAGE_SHIFT)))
+		return -EFBIG;
+
+	vma->vm_ops = &ncp_file_mmap;
+	file_accessed(file);
+	return 0;
+}