v4.19.13 snapshot.
diff --git a/fs/romfs/mmap-nommu.c b/fs/romfs/mmap-nommu.c
new file mode 100644
index 0000000..1118a0d
--- /dev/null
+++ b/fs/romfs/mmap-nommu.c
@@ -0,0 +1,89 @@
+/* NOMMU mmap support for RomFS on MTD devices
+ *
+ * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/mm.h>
+#include <linux/mtd/super.h>
+#include "internal.h"
+
+/*
+ * try to determine where a shared mapping can be made
+ * - only supported for NOMMU at the moment (MMU can't doesn't copy private
+ * mappings)
+ * - attempts to map through to the underlying MTD device
+ */
+static unsigned long romfs_get_unmapped_area(struct file *file,
+ unsigned long addr,
+ unsigned long len,
+ unsigned long pgoff,
+ unsigned long flags)
+{
+ struct inode *inode = file->f_mapping->host;
+ struct mtd_info *mtd = inode->i_sb->s_mtd;
+ unsigned long isize, offset, maxpages, lpages;
+ int ret;
+
+ if (!mtd)
+ return (unsigned long) -ENOSYS;
+
+ /* the mapping mustn't extend beyond the EOF */
+ lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ isize = i_size_read(inode);
+ offset = pgoff << PAGE_SHIFT;
+
+ maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
+ return (unsigned long) -EINVAL;
+
+ if (addr != 0)
+ return (unsigned long) -EINVAL;
+
+ if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
+ return (unsigned long) -EINVAL;
+
+ offset += ROMFS_I(inode)->i_dataoffset;
+ if (offset >= mtd->size)
+ return (unsigned long) -EINVAL;
+ /* the mapping mustn't extend beyond the EOF */
+ if ((offset + len) > mtd->size)
+ len = mtd->size - offset;
+
+ ret = mtd_get_unmapped_area(mtd, len, offset, flags);
+ if (ret == -EOPNOTSUPP)
+ ret = -ENOSYS;
+ return (unsigned long) ret;
+}
+
+/*
+ * permit a R/O mapping to be made directly through onto an MTD device if
+ * possible
+ */
+static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
+}
+
+static unsigned romfs_mmap_capabilities(struct file *file)
+{
+ struct mtd_info *mtd = file_inode(file)->i_sb->s_mtd;
+
+ if (!mtd)
+ return NOMMU_MAP_COPY;
+ return mtd_mmap_capabilities(mtd);
+}
+
+const struct file_operations romfs_ro_fops = {
+ .llseek = generic_file_llseek,
+ .read_iter = generic_file_read_iter,
+ .splice_read = generic_file_splice_read,
+ .mmap = romfs_mmap,
+ .get_unmapped_area = romfs_get_unmapped_area,
+ .mmap_capabilities = romfs_mmap_capabilities,
+};