fs-verity: add data verification hooks for ->readpages()

Add functions that verify data pages that have been read from a
fs-verity file, against that file's Merkle tree.  These will be called
from filesystems' ->readpage() and ->readpages() methods.

Since data verification can block, a workqueue is provided for these
methods to enqueue verification work from their bio completion callback.

See the "Verifying data" section of
Documentation/filesystems/fsverity.rst for more information.

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/verity/open.c b/fs/verity/open.c
index 2cb2fe8082bf..3636a1ed8e2c 100644
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -337,3 +337,9 @@ int __init fsverity_init_info_cache(void)
 		return -ENOMEM;
 	return 0;
 }
+
+void __init fsverity_exit_info_cache(void)
+{
+	kmem_cache_destroy(fsverity_info_cachep);
+	fsverity_info_cachep = NULL;
+}