[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);