[MTD] generalise the handling of MTD-specific superblocks

Generalise the handling of MTD-specific superblocks so that JFFS2 and ROMFS
can both share it.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

2 files changed, 233 insertions, 2 deletions

diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
index 92055405cb30..451adcc52b3c 100644
--- a/drivers/mtd/Makefile
+++ b/drivers/mtd/Makefile
@@ -1,10 +1,9 @@
 #
 # Makefile for the memory technology device drivers.
 #
-# $Id: Makefile.common,v 1.7 2005/07/11 10:39:27 gleixner Exp $
 
 # Core functionality.
-mtd-y				:= mtdcore.o
+mtd-y				:= mtdcore.o mtdsuper.o
 mtd-$(CONFIG_MTD_PARTITIONS)	+= mtdpart.o
 obj-$(CONFIG_MTD)		+= $(mtd-y)
 
diff --git a/drivers/mtd/mtdsuper.c b/drivers/mtd/mtdsuper.c
new file mode 100644
index 000000000000..a279540ba87a
--- /dev/null
+++ b/drivers/mtd/mtdsuper.c
@@ -0,0 +1,232 @@
+/* MTD-based superblock management
+ *
+ * Copyright © 2001-2007 Red Hat, Inc. All Rights Reserved.
+ * 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/ctype.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) {
+		DEBUG(2, "MTDSB: Match on device %d (\"%s\")\n",
+		      mtd->index, mtd->name);
+		return 1;
+	}
+
+	DEBUG(2, "MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n",
+	      sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name);
+	return 0;
+}
+
+/*
+ * 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);
+	return 0;
+}
+
+/*
+ * get a superblock on an MTD-backed filesystem
+ */
+static int get_sb_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 vfsmount *mnt)
+{
+	struct super_block *sb;
+	int ret;
+
+	sb = sget(fs_type, get_sb_mtd_compare, get_sb_mtd_set, mtd);
+	if (IS_ERR(sb))
+		goto out_error;
+
+	if (sb->s_root)
+		goto already_mounted;
+
+	/* fresh new superblock */
+	DEBUG(1, "MTDSB: New superblock for device %d (\"%s\")\n",
+	      mtd->index, mtd->name);
+
+	ret = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
+	if (ret < 0) {
+		up_write(&sb->s_umount);
+		deactivate_super(sb);
+		return ret;
+	}
+
+	/* go */
+	sb->s_flags |= MS_ACTIVE;
+	return simple_set_mnt(mnt, sb);
+
+	/* new mountpoint for an already mounted superblock */
+already_mounted:
+	DEBUG(1, "MTDSB: Device %d (\"%s\") is already mounted\n",
+	      mtd->index, mtd->name);
+	ret = simple_set_mnt(mnt, sb);
+	goto out_put;
+
+out_error:
+	ret = PTR_ERR(sb);
+out_put:
+	put_mtd_device(mtd);
+	return ret;
+}
+
+/*
+ * get a superblock on an MTD-backed filesystem by MTD device number
+ */
+static int get_sb_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 vfsmount *mnt)
+{
+	struct mtd_info *mtd;
+
+	mtd = get_mtd_device(NULL, mtdnr);
+	if (!mtd) {
+		DEBUG(0, "MTDSB: Device #%u doesn't appear to exist\n", mtdnr);
+		return -EINVAL;
+	}
+
+	return get_sb_mtd_aux(fs_type, flags, dev_name, data, mtd, fill_super,
+			      mnt);
+}
+
+/*
+ * set up an MTD-based superblock
+ */
+int get_sb_mtd(struct file_system_type *fs_type, int flags,
+	       const char *dev_name, void *data,
+	       int (*fill_super)(struct super_block *, void *, int),
+	       struct vfsmount *mnt)
+{
+	struct nameidata nd;
+	int mtdnr, ret;
+
+	if (!dev_name)
+		return -EINVAL;
+
+	DEBUG(2, "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 */
+			DEBUG(1, "MTDSB: mtd:%%s, name \"%s\"\n",
+			      dev_name + 4);
+
+			for (mtdnr = 0; mtdnr < MAX_MTD_DEVICES; mtdnr++) {
+				mtd = get_mtd_device(NULL, mtdnr);
+				if (mtd) {
+					if (!strcmp(mtd->name, dev_name + 4))
+						return get_sb_mtd_aux(
+							fs_type, flags,
+							dev_name, data, mtd,
+							fill_super, mnt);
+
+					put_mtd_device(mtd);
+				}
+			}
+
+			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 */
+				DEBUG(1, "MTDSB: mtd%%d, mtdnr %d\n",
+				      mtdnr);
+				return get_sb_mtd_nr(fs_type, flags,
+						     dev_name, data,
+						     mtdnr, fill_super, mnt);
+			}
+		}
+	}
+
+	/* try the old way - the hack where we allowed users to mount
+	 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
+	 */
+	ret = path_lookup(dev_name, LOOKUP_FOLLOW, &nd);
+
+	DEBUG(1, "MTDSB: path_lookup() returned %d, inode %p\n",
+	      ret, nd.dentry ? nd.dentry->d_inode : NULL);
+
+	if (ret)
+		return ret;
+
+	ret = -EINVAL;
+
+	if (!S_ISBLK(nd.dentry->d_inode->i_mode))
+		goto out;
+
+	if (nd.mnt->mnt_flags & MNT_NODEV) {
+		ret = -EACCES;
+		goto out;
+	}
+
+	if (imajor(nd.dentry->d_inode) != MTD_BLOCK_MAJOR)
+		goto not_an_MTD_device;
+
+	mtdnr = iminor(nd.dentry->d_inode);
+	path_release(&nd);
+
+	return get_sb_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super,
+			     mnt);
+
+not_an_MTD_device:
+	if (!(flags & MS_SILENT))
+		printk(KERN_NOTICE
+		       "MTD: Attempt to mount non-MTD device \"%s\"\n",
+		       dev_name);
+out:
+	path_release(&nd);
+	return ret;
+
+}
+
+EXPORT_SYMBOL_GPL(get_sb_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);