[PATCH v7 02/22] fsverity: expose ensure_fsverity_info()

[Andrey Albershteyn <aalbersh@kernel.org>]

This function will be used by XFS's scrub to force fsverity activation,
therefore, to read fsverity context.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Acked-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
---
 fs/verity/open.c         | 22 ++++++++++++++++++++--
 include/linux/fsverity.h |  2 ++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/fs/verity/open.c b/fs/verity/open.c
index dfa0d1afe0fe..d32d0899df25 100644
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -344,7 +344,24 @@ int fsverity_get_descriptor(struct inode *inode,
 	return 0;
 }
 
-static int ensure_verity_info(struct inode *inode)
+/**
+ * fsverity_ensure_verity_info() - cache verity info if it's not already cached
+ * @inode: the inode for which verity info should be cached
+ *
+ * Ensure this inode has verity info attached to it, it's assumed the inode
+ * already has fsverity enabled. Read fsverity descriptor and creates verity
+ * based on that.
+ *
+ * This needs to be called at least once before any of the inode's data
+ * can be verified (and thus read at all) or the inode's fsverity digest
+ * retrieved.  fsverity_file_open() calls this already, which handles
+ * normal file accesses.  If a filesystem does any internal (i.e. not
+ * associated with a file descriptor) reads of the file's data or
+ * fsverity digest, it must call this explicitly before doing so.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+int fsverity_ensure_verity_info(struct inode *inode)
 {
 	struct fsverity_info *vi = fsverity_get_info(inode), *found;
 	struct fsverity_descriptor *desc;
@@ -380,12 +397,13 @@ static int ensure_verity_info(struct inode *inode)
 	kfree(desc);
 	return err;
 }
+EXPORT_SYMBOL_GPL(fsverity_ensure_verity_info);
 
 int __fsverity_file_open(struct inode *inode, struct file *filp)
 {
 	if (filp->f_mode & FMODE_WRITE)
 		return -EPERM;
-	return ensure_verity_info(inode);
+	return fsverity_ensure_verity_info(inode);
 }
 EXPORT_SYMBOL_GPL(__fsverity_file_open);
 
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index a8f9aa75b792..5562271bd628 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -309,6 +309,8 @@ static inline int fsverity_file_open(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+int fsverity_ensure_verity_info(struct inode *inode);
+
 void fsverity_cleanup_inode(struct inode *inode);
 
 struct page *generic_read_merkle_tree_page(struct inode *inode, pgoff_t index);
-- 
2.51.2