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

4 files changed, 107 insertions, 7 deletions

diff --git a/fs/fs_context.c b/fs/fs_context.c
index 103643c68e3f..87c2c9687d90 100644
--- a/fs/fs_context.c
+++ b/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;
 	}
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 3cf4f6aa48d6..2c215171c0eb 100644
--- a/fs/nfsd/nfsctl.c
+++ b/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)
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 33f72d1b92cc..0b7c8dffc9ae 100644
--- a/fs/proc/root.c
+++ b/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)
diff --git a/fs/super.c b/fs/super.c
index 5960578a4076..da223b4cfbca 100644
--- a/fs/super.c
+++ b/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;