[RFC PATCH 5/8] btrfs: super: Introduce btrfs_dup_fc

[Marcos Paulo de Souza <marcos@mpdesouza.com>]

From: Marcos Paulo de Souza <mpdesouza@suse.com>

This function will be used in a future patch when mounting root filesystem
before mounting a subvolume.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
---
 fs/btrfs/super.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 88221d1d8bae..6b70fb73a1ea 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1091,6 +1091,56 @@ static int btrfs_fc_validate(struct fs_context *fc)
 	return 0;
 }
 
+static int btrfs_dup_fc(struct fs_context *fc, struct fs_context *src_fc)
+{
+	int i;
+	struct btrfs_fs_context *ctx, *src = src_fc->fs_private;
+
+	ctx = kmemdup(src, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->subvol_name = NULL;
+	ctx->devices = NULL;
+	ctx->root_mnt = NULL;
+
+	if (src->subvol_name) {
+		ctx->subvol_name = kstrdup(src->subvol_name, GFP_KERNEL);
+		if (!ctx->subvol_name)
+			goto nomem_ctx;
+	}
+
+	if (ctx->nr_devices) {
+		ctx->devices = kcalloc(ctx->nr_devices, sizeof(char *), GFP_KERNEL);
+		if (!ctx->devices)
+			goto nomem_sub;
+		for (i = 0; i < ctx->nr_devices; i++) {
+			ctx->devices[i] = kstrdup(src->devices[i], GFP_KERNEL);
+			if (!ctx->devices[i])
+				goto nomem_devs;
+		}
+	}
+
+	if (src_fc->source) {
+		fc->source = kstrdup(src_fc->source, GFP_KERNEL);
+		if (!fc->source)
+			goto nomem_devs;
+	}
+
+	fc->fs_private = ctx;
+	return 0;
+
+nomem_devs:
+	for (i = 0; i < ctx->nr_devices; i++)
+		kfree(ctx->devices[i]);
+	kfree(ctx->devices);
+nomem_sub:
+	kfree(ctx->subvol_name);
+nomem_ctx:
+	kfree(ctx);
+	return -ENOMEM;
+}
+
 static int btrfs_fc_parse_param(struct fs_context *fc, struct fs_parameter *param)
 {
 	int opt;
@@ -2967,6 +3017,7 @@ static void btrfs_fc_free(struct fs_context *fc)
 }
 
 static const struct fs_context_operations btrfs_context_ops = {
+	.dup = btrfs_dup_fc,
 	.free = btrfs_fc_free,
 	.parse_param = btrfs_fc_parse_param,
 };
-- 
2.28.0