[PATCH 13/40] fsverity: expose merkle tree geometry to callers

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Create a function that will return selected information about the
geometry of the merkle tree.  Online fsck for XFS will need this piece
to perform basic checks of the merkle tree.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/verity/open.c         |   26 ++++++++++++++++++++++++++
 include/linux/fsverity.h |    3 +++
 2 files changed, 29 insertions(+)


diff --git a/fs/verity/open.c b/fs/verity/open.c
index 9603b3a404f7..7a86407732c4 100644
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -412,6 +412,32 @@ void __fsverity_cleanup_inode(struct inode *inode)
 }
 EXPORT_SYMBOL_GPL(__fsverity_cleanup_inode);
 
+/**
+ * fsverity_merkle_tree_geometry() - return Merkle tree geometry
+ * @inode: the inode for which the Merkle tree is being built
+ * @block_size: size of a merkle tree block, in bytes
+ * @tree_size: size of the merkle tree, in bytes
+ */
+int fsverity_merkle_tree_geometry(struct inode *inode, unsigned int *block_size,
+				  u64 *tree_size)
+{
+	struct fsverity_info *vi;
+	int error;
+
+	if (!IS_VERITY(inode))
+		return -EOPNOTSUPP;
+
+	error = ensure_verity_info(inode);
+	if (error)
+		return error;
+
+	vi = fsverity_get_info(inode);
+	*block_size = vi->tree_params.block_size;
+	*tree_size = vi->tree_params.tree_size;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fsverity_merkle_tree_geometry);
+
 void __init fsverity_init_info_cache(void)
 {
 	fsverity_info_cachep = KMEM_CACHE_USERCOPY(
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index c5f3564f2cb8..17bc0729119c 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -240,6 +240,9 @@ int __fsverity_file_open(struct inode *inode, struct file *filp);
 int __fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr);
 void __fsverity_cleanup_inode(struct inode *inode);
 
+int fsverity_merkle_tree_geometry(struct inode *inode, unsigned int *block_size,
+				  u64 *tree_size);
+
 /**
  * fsverity_cleanup_inode() - free the inode's verity info, if present
  * @inode: an inode being evicted