v4.19.13 snapshot.
diff --git a/drivers/mtd/mtdsuper.c b/drivers/mtd/mtdsuper.c
new file mode 100644
index 0000000..d58a61c
--- /dev/null
+++ b/drivers/mtd/mtdsuper.c
@@ -0,0 +1,224 @@
+/* MTD-based superblock management
+ *
+ * Copyright © 2001-2007 Red Hat, Inc. All Rights Reserved.
+ * Copyright © 2001-2010 David Woodhouse <dwmw2@infradead.org>
+ *
+ * Written by: David Howells <dhowells@redhat.com>
+ * David Woodhouse <dwmw2@infradead.org>
+ *
+ * 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/mtd/super.h>
+#include <linux/namei.h>
+#include <linux/export.h>
+#include <linux/ctype.h>
+#include <linux/slab.h>
+#include <linux/major.h>
+#include <linux/backing-dev.h>
+
+/*
+ * compare superblocks to see if they're equivalent
+ * - they are if the underlying MTD device is the same
+ */
+static int get_sb_mtd_compare(struct super_block *sb, void *_mtd)
+{
+ struct mtd_info *mtd = _mtd;
+
+ if (sb->s_mtd == mtd) {
+ pr_debug("MTDSB: Match on device %d (\"%s\")\n",
+ mtd->index, mtd->name);
+ return 1;
+ }
+
+ pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n",
+ sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name);
+ return 0;
+}
+
+extern struct backing_dev_info *mtd_bdi;
+
+/*
+ * mark the superblock by the MTD device it is using
+ * - set the device number to be the correct MTD block device for pesuperstence
+ * of NFS exports
+ */
+static int get_sb_mtd_set(struct super_block *sb, void *_mtd)
+{
+ struct mtd_info *mtd = _mtd;
+
+ sb->s_mtd = mtd;
+ sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, mtd->index);
+ sb->s_bdi = bdi_get(mtd_bdi);
+
+ return 0;
+}
+
+/*
+ * get a superblock on an MTD-backed filesystem
+ */
+static struct dentry *mount_mtd_aux(struct file_system_type *fs_type, int flags,
+ const char *dev_name, void *data,
+ struct mtd_info *mtd,
+ int (*fill_super)(struct super_block *, void *, int))
+{
+ struct super_block *sb;
+ int ret;
+
+ sb = sget(fs_type, get_sb_mtd_compare, get_sb_mtd_set, flags, mtd);
+ if (IS_ERR(sb))
+ goto out_error;
+
+ if (sb->s_root)
+ goto already_mounted;
+
+ /* fresh new superblock */
+ pr_debug("MTDSB: New superblock for device %d (\"%s\")\n",
+ mtd->index, mtd->name);
+
+ ret = fill_super(sb, data, flags & SB_SILENT ? 1 : 0);
+ if (ret < 0) {
+ deactivate_locked_super(sb);
+ return ERR_PTR(ret);
+ }
+
+ /* go */
+ sb->s_flags |= SB_ACTIVE;
+ return dget(sb->s_root);
+
+ /* new mountpoint for an already mounted superblock */
+already_mounted:
+ pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n",
+ mtd->index, mtd->name);
+ put_mtd_device(mtd);
+ return dget(sb->s_root);
+
+out_error:
+ put_mtd_device(mtd);
+ return ERR_CAST(sb);
+}
+
+/*
+ * get a superblock on an MTD-backed filesystem by MTD device number
+ */
+static struct dentry *mount_mtd_nr(struct file_system_type *fs_type, int flags,
+ const char *dev_name, void *data, int mtdnr,
+ int (*fill_super)(struct super_block *, void *, int))
+{
+ struct mtd_info *mtd;
+
+ mtd = get_mtd_device(NULL, mtdnr);
+ if (IS_ERR(mtd)) {
+ pr_debug("MTDSB: Device #%u doesn't appear to exist\n", mtdnr);
+ return ERR_CAST(mtd);
+ }
+
+ return mount_mtd_aux(fs_type, flags, dev_name, data, mtd, fill_super);
+}
+
+/*
+ * set up an MTD-based superblock
+ */
+struct dentry *mount_mtd(struct file_system_type *fs_type, int flags,
+ const char *dev_name, void *data,
+ int (*fill_super)(struct super_block *, void *, int))
+{
+#ifdef CONFIG_BLOCK
+ struct block_device *bdev;
+ int ret, major;
+#endif
+ int mtdnr;
+
+ if (!dev_name)
+ return ERR_PTR(-EINVAL);
+
+ pr_debug("MTDSB: dev_name \"%s\"\n", dev_name);
+
+ /* the preferred way of mounting in future; especially when
+ * CONFIG_BLOCK=n - we specify the underlying MTD device by number or
+ * by name, so that we don't require block device support to be present
+ * in the kernel. */
+ if (dev_name[0] == 'm' && dev_name[1] == 't' && dev_name[2] == 'd') {
+ if (dev_name[3] == ':') {
+ struct mtd_info *mtd;
+
+ /* mount by MTD device name */
+ pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
+ dev_name + 4);
+
+ mtd = get_mtd_device_nm(dev_name + 4);
+ if (!IS_ERR(mtd))
+ return mount_mtd_aux(
+ fs_type, flags,
+ dev_name, data, mtd,
+ fill_super);
+
+ printk(KERN_NOTICE "MTD:"
+ " MTD device with name \"%s\" not found.\n",
+ dev_name + 4);
+
+ } else if (isdigit(dev_name[3])) {
+ /* mount by MTD device number name */
+ char *endptr;
+
+ mtdnr = simple_strtoul(dev_name + 3, &endptr, 0);
+ if (!*endptr) {
+ /* It was a valid number */
+ pr_debug("MTDSB: mtd%%d, mtdnr %d\n",
+ mtdnr);
+ return mount_mtd_nr(fs_type, flags,
+ dev_name, data,
+ mtdnr, fill_super);
+ }
+ }
+ }
+
+#ifdef CONFIG_BLOCK
+ /* try the old way - the hack where we allowed users to mount
+ * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
+ */
+ bdev = lookup_bdev(dev_name);
+ if (IS_ERR(bdev)) {
+ ret = PTR_ERR(bdev);
+ pr_debug("MTDSB: lookup_bdev() returned %d\n", ret);
+ return ERR_PTR(ret);
+ }
+ pr_debug("MTDSB: lookup_bdev() returned 0\n");
+
+ ret = -EINVAL;
+
+ major = MAJOR(bdev->bd_dev);
+ mtdnr = MINOR(bdev->bd_dev);
+ bdput(bdev);
+
+ if (major != MTD_BLOCK_MAJOR)
+ goto not_an_MTD_device;
+
+ return mount_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super);
+
+not_an_MTD_device:
+#endif /* CONFIG_BLOCK */
+
+ if (!(flags & SB_SILENT))
+ printk(KERN_NOTICE
+ "MTD: Attempt to mount non-MTD device \"%s\"\n",
+ dev_name);
+ return ERR_PTR(-EINVAL);
+}
+
+EXPORT_SYMBOL_GPL(mount_mtd);
+
+/*
+ * destroy an MTD-based superblock
+ */
+void kill_mtd_super(struct super_block *sb)
+{
+ generic_shutdown_super(sb);
+ put_mtd_device(sb->s_mtd);
+ sb->s_mtd = NULL;
+}
+
+EXPORT_SYMBOL_GPL(kill_mtd_super);