Merge branch 'work.mount-base' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs mount API infrastructure updates from Al Viro:
 "Infrastructure bits of mount API conversions.

  The rest is more of per-filesystem updates and that will happen
  in separate pull requests"

* 'work.mount-base' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  mtd: Provide fs_context-aware mount_mtd() replacement
  vfs: Create fs_context-aware mount_bdev() replacement
  new helper: get_tree_keyed()
  vfs: set fs_context::user_ns for reconfigure

drivers/mtd/mtdcore.h

@@ -5,6 +5,7 @@
  */
 
 extern struct mutex mtd_table_mutex;
+extern struct backing_dev_info *mtd_bdi;
 
 struct mtd_info *__mtd_next_device(int i);
 int __must_check add_mtd_device(struct mtd_info *mtd);

drivers/mtd/mtdsuper.c

@@ -15,6 +15,183 @@
 #include <linux/slab.h>
 #include <linux/major.h>
 #include <linux/backing-dev.h>
+#include <linux/fs_context.h>
+#include "mtdcore.h"
+
+/*
+ * compare superblocks to see if they're equivalent
+ * - they are if the underlying MTD device is the same
+ */
+static int mtd_test_super(struct super_block *sb, struct fs_context *fc)
+{
+	struct mtd_info *mtd = fc->sget_key;
+
+	if (sb->s_mtd == fc->sget_key) {
+		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;
+}
+
+/*
+ * 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 mtd_set_super(struct super_block *sb, struct fs_context *fc)
+{
+	sb->s_mtd = fc->sget_key;
+	sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
+	sb->s_bdi = bdi_get(mtd_bdi);
+	return 0;
+}
+
+/*
+ * get a superblock on an MTD-backed filesystem
+ */
+static int mtd_get_sb(struct fs_context *fc,
+		      struct mtd_info *mtd,
+		      int (*fill_super)(struct super_block *,
+					struct fs_context *))
+{
+	struct super_block *sb;
+	int ret;
+
+	fc->sget_key = mtd;
+	sb = sget_fc(fc, mtd_test_super, mtd_set_super);
+	if (IS_ERR(sb))
+		return PTR_ERR(sb);
+
+	if (sb->s_root) {
+		/* new mountpoint for an already mounted superblock */
+		pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n",
+			 mtd->index, mtd->name);
+		put_mtd_device(mtd);
+	} else {
+		/* fresh new superblock */
+		pr_debug("MTDSB: New superblock for device %d (\"%s\")\n",
+			 mtd->index, mtd->name);
+
+		ret = fill_super(sb, fc);
+		if (ret < 0)
+			goto error_sb;
+
+		sb->s_flags |= SB_ACTIVE;
+	}
+
+	BUG_ON(fc->root);
+	fc->root = dget(sb->s_root);
+	return 0;
+
+error_sb:
+	deactivate_locked_super(sb);
+	return ret;
+}
+
+/*
+ * get a superblock on an MTD-backed filesystem by MTD device number
+ */
+static int mtd_get_sb_by_nr(struct fs_context *fc, int mtdnr,
+			    int (*fill_super)(struct super_block *,
+					      struct fs_context *))
+{
+	struct mtd_info *mtd;
+
+	mtd = get_mtd_device(NULL, mtdnr);
+	if (IS_ERR(mtd)) {
+		errorf(fc, "MTDSB: Device #%u doesn't appear to exist\n", mtdnr);
+		return PTR_ERR(mtd);
+	}
+
+	return mtd_get_sb(fc, mtd, fill_super);
+}
+
+/**
+ * get_tree_mtd - Get a superblock based on a single MTD device
+ * @fc: The filesystem context holding the parameters
+ * @fill_super: Helper to initialise a new superblock
+ */
+int get_tree_mtd(struct fs_context *fc,
+	      int (*fill_super)(struct super_block *sb,
+				struct fs_context *fc))
+{
+#ifdef CONFIG_BLOCK
+	struct block_device *bdev;
+	int ret, major;
+#endif
+	int mtdnr;
+
+	if (!fc->source)
+		return invalf(fc, "No source specified");
+
+	pr_debug("MTDSB: dev_name \"%s\"\n", fc->source);
+
+	/* 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 (fc->source[0] == 'm' &&
+	    fc->source[1] == 't' &&
+	    fc->source[2] == 'd') {
+		if (fc->source[3] == ':') {
+			struct mtd_info *mtd;
+
+			/* mount by MTD device name */
+			pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
+				 fc->source + 4);
+
+			mtd = get_mtd_device_nm(fc->source + 4);
+			if (!IS_ERR(mtd))
+				return mtd_get_sb(fc, mtd, fill_super);
+
+			errorf(fc, "MTD: MTD device with name \"%s\" not found",
+			       fc->source + 4);
+
+		} else if (isdigit(fc->source[3])) {
+			/* mount by MTD device number name */
+			char *endptr;
+
+			mtdnr = simple_strtoul(fc->source + 3, &endptr, 0);
+			if (!*endptr) {
+				/* It was a valid number */
+				pr_debug("MTDSB: mtd%%d, mtdnr %d\n", mtdnr);
+				return mtd_get_sb_by_nr(fc, 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(fc->source);
+	if (IS_ERR(bdev)) {
+		ret = PTR_ERR(bdev);
+		errorf(fc, "MTD: Couldn't look up '%s': %d", fc->source, ret);
+		return ret;
+	}
+	pr_debug("MTDSB: lookup_bdev() returned 0\n");
+
+	major = MAJOR(bdev->bd_dev);
+	mtdnr = MINOR(bdev->bd_dev);
+	bdput(bdev);
+
+	if (major == MTD_BLOCK_MAJOR)
+		return mtd_get_sb_by_nr(fc, mtdnr, fill_super);
+
+#endif /* CONFIG_BLOCK */
+
+	if (!(fc->sb_flags & SB_SILENT))
+		errorf(fc, "MTD: Attempt to mount non-MTD device \"%s\"",
+		       fc->source);
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(get_tree_mtd);
 
 /*
  * compare superblocks to see if they're equivalent
@@ -35,8 +212,6 @@ static int get_sb_mtd_compare(struct super_block *sb, void *_mtd)
 	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

fs/fs_context.c

@@ -279,10 +279,8 @@ static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
 		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
 		break;
 	case FS_CONTEXT_FOR_RECONFIGURE:
-		/* We don't pin any namespaces as the superblock's
-		 * subscriptions cannot be changed at this point.
-		 */
 		atomic_inc(&reference->d_sb->s_active);
+		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
 		fc->root = dget(reference);
 		break;
 	}

fs/nfsd/nfsctl.c

@@ -1385,8 +1385,7 @@ static int nfsd_fill_super(struct super_block *sb, struct fs_context *fc)
 
 static int nfsd_fs_get_tree(struct fs_context *fc)
 {
-	fc->s_fs_info = get_net(fc->net_ns);
-	return vfs_get_super(fc, vfs_get_keyed_super, nfsd_fill_super);
+	return get_tree_keyed(fc, nfsd_fill_super, get_net(fc->net_ns));
 }
 
 static void nfsd_fs_free_fc(struct fs_context *fc)

fs/proc/root.c

@@ -157,8 +157,7 @@ static int proc_get_tree(struct fs_context *fc)
 {
 	struct proc_fs_context *ctx = fc->fs_private;
 
-	fc->s_fs_info = ctx->pid_ns;
-	return vfs_get_super(fc, vfs_get_keyed_super, proc_fill_super);
+	return get_tree_keyed(fc, proc_fill_super, ctx->pid_ns);
 }
 
 static void proc_fs_context_free(struct fs_context *fc)

fs/super.c

@@ -1211,7 +1211,18 @@ int get_tree_single(struct fs_context *fc,
 }
 EXPORT_SYMBOL(get_tree_single);
 
+int get_tree_keyed(struct fs_context *fc,
+		  int (*fill_super)(struct super_block *sb,
+				    struct fs_context *fc),
+		void *key)
+{
+	fc->s_fs_info = key;
+	return vfs_get_super(fc, vfs_get_keyed_super, fill_super);
+}
+EXPORT_SYMBOL(get_tree_keyed);
+
 #ifdef CONFIG_BLOCK
+
 static int set_bdev_super(struct super_block *s, void *data)
 {
 	s->s_bdev = data;
@@ -1221,6 +1232,99 @@ static int set_bdev_super(struct super_block *s, void *data)
 	return 0;
 }
 
+static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)
+{
+	return set_bdev_super(s, fc->sget_key);
+}
+
+static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)
+{
+	return s->s_bdev == fc->sget_key;
+}
+
+/**
+ * get_tree_bdev - Get a superblock based on a single block device
+ * @fc: The filesystem context holding the parameters
+ * @fill_super: Helper to initialise a new superblock
+ */
+int get_tree_bdev(struct fs_context *fc,
+		int (*fill_super)(struct super_block *,
+				  struct fs_context *))
+{
+	struct block_device *bdev;
+	struct super_block *s;
+	fmode_t mode = FMODE_READ | FMODE_EXCL;
+	int error = 0;
+
+	if (!(fc->sb_flags & SB_RDONLY))
+		mode |= FMODE_WRITE;
+
+	if (!fc->source)
+		return invalf(fc, "No source specified");
+
+	bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
+	if (IS_ERR(bdev)) {
+		errorf(fc, "%s: Can't open blockdev", fc->source);
+		return PTR_ERR(bdev);
+	}
+
+	/* Once the superblock is inserted into the list by sget_fc(), s_umount
+	 * will protect the lockfs code from trying to start a snapshot while
+	 * we are mounting
+	 */
+	mutex_lock(&bdev->bd_fsfreeze_mutex);
+	if (bdev->bd_fsfreeze_count > 0) {
+		mutex_unlock(&bdev->bd_fsfreeze_mutex);
+		warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
+		return -EBUSY;
+	}
+
+	fc->sb_flags |= SB_NOSEC;
+	fc->sget_key = bdev;
+	s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);
+	mutex_unlock(&bdev->bd_fsfreeze_mutex);
+	if (IS_ERR(s))
+		return PTR_ERR(s);
+
+	if (s->s_root) {
+		/* Don't summarily change the RO/RW state. */
+		if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
+			warnf(fc, "%pg: Can't mount, would change RO state", bdev);
+			deactivate_locked_super(s);
+			blkdev_put(bdev, mode);
+			return -EBUSY;
+		}
+
+		/*
+		 * s_umount nests inside bd_mutex during
+		 * __invalidate_device().  blkdev_put() acquires
+		 * bd_mutex and can't be called under s_umount.  Drop
+		 * s_umount temporarily.  This is safe as we're
+		 * holding an active reference.
+		 */
+		up_write(&s->s_umount);
+		blkdev_put(bdev, mode);
+		down_write(&s->s_umount);
+	} else {
+		s->s_mode = mode;
+		snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
+		sb_set_blocksize(s, block_size(bdev));
+		error = fill_super(s, fc);
+		if (error) {
+			deactivate_locked_super(s);
+			return error;
+		}
+
+		s->s_flags |= SB_ACTIVE;
+		bdev->bd_super = s;
+	}
+
+	BUG_ON(fc->root);
+	fc->root = dget(s->s_root);
+	return 0;
+}
+EXPORT_SYMBOL(get_tree_bdev);
+
 static int test_bdev_super(struct super_block *s, void *data)
 {
 	return (void *)s->s_bdev == data;

include/linux/fs_context.h

@@ -88,6 +88,7 @@ struct fs_context {
 	struct mutex		uapi_mutex;	/* Userspace access mutex */
 	struct file_system_type	*fs_type;
 	void			*fs_private;	/* The filesystem's context */
+	void			*sget_key;
 	struct dentry		*root;		/* The root and superblock */
 	struct user_namespace	*user_ns;	/* The user namespace for this mount */
 	struct net		*net_ns;	/* The network namespace for this mount */
@@ -136,7 +137,7 @@ extern int vfs_get_tree(struct fs_context *fc);
 extern void put_fs_context(struct fs_context *fc);
 
 /*
- * sget() wrapper to be called from the ->get_tree() op.
+ * sget() wrappers to be called from the ->get_tree() op.
  */
 enum vfs_get_super_keying {
 	vfs_get_single_super,	/* Only one such superblock may exist */
@@ -147,12 +148,21 @@ extern int vfs_get_super(struct fs_context *fc,
 			 enum vfs_get_super_keying keying,
 			 int (*fill_super)(struct super_block *sb,
 					   struct fs_context *fc));
+
 extern int get_tree_nodev(struct fs_context *fc,
 			 int (*fill_super)(struct super_block *sb,
 					   struct fs_context *fc));
 extern int get_tree_single(struct fs_context *fc,
 			 int (*fill_super)(struct super_block *sb,
 					   struct fs_context *fc));
+extern int get_tree_keyed(struct fs_context *fc,
+			 int (*fill_super)(struct super_block *sb,
+					   struct fs_context *fc),
+			 void *key);
+
+extern int get_tree_bdev(struct fs_context *fc,
+			       int (*fill_super)(struct super_block *sb,
+						 struct fs_context *fc));
 
 extern const struct file_operations fscontext_fops;
 

include/linux/mtd/super.h

@@ -14,6 +14,9 @@
 #include <linux/fs.h>
 #include <linux/mount.h>
 
+extern int get_tree_mtd(struct fs_context *fc,
+		     int (*fill_super)(struct super_block *sb,
+				       struct fs_context *fc));
 extern 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));

ipc/mqueue.c

@@ -364,8 +364,7 @@ static int mqueue_get_tree(struct fs_context *fc)
 {
 	struct mqueue_fs_context *ctx = fc->fs_private;
 
-	fc->s_fs_info = ctx->ipc_ns;
-	return vfs_get_super(fc, vfs_get_keyed_super, mqueue_fill_super);
+	return get_tree_keyed(fc, mqueue_fill_super, ctx->ipc_ns);
 }
 
 static void mqueue_fs_context_free(struct fs_context *fc)

net/sunrpc/rpc_pipe.c

@@ -1416,8 +1416,7 @@ EXPORT_SYMBOL_GPL(gssd_running);
 
 static int rpc_fs_get_tree(struct fs_context *fc)
 {
-	fc->s_fs_info = get_net(fc->net_ns);
-	return vfs_get_super(fc, vfs_get_keyed_super, rpc_fill_super);
+	return get_tree_keyed(fc, rpc_fill_super, get_net(fc->net_ns));
 }
 
 static void rpc_fs_free_fc(struct fs_context *fc)