[PATCH v4 04/17] fscrypt: add ->ci_inode to fscrypt_info

[Eric Biggers <ebiggers@kernel.org>]

From: Eric Biggers <ebiggers@google.com>

Add an inode back-pointer to 'struct fscrypt_info', such that
inode->i_crypt_info->ci_inode = inode.

This will be useful for:

1. Evicting the inodes when a fscrypt key is removed, since we'll track
   the inodes using a given key by linking their fscrypt_infos together,
   rather than the inodes directly.  This avoids bloating 'struct inode'
   with a new list_head.

2. Simplifying the per-file key setup, since the inode pointer won't
   have to be passed around everywhere just in case something goes wrong
   and it's needed for fscrypt_warn().

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/fscrypt_private.h | 3 +++
 fs/crypto/keyinfo.c         | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 52e09ef40bfa6..ac24edfc297f1 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -73,6 +73,9 @@ struct fscrypt_info {
 	 */
 	struct fscrypt_mode *ci_mode;
 
+	/* Back-pointer to the inode */
+	struct inode *ci_inode;
+
 	/*
 	 * If non-NULL, then this inode uses a master key directly rather than a
 	 * derived key, and ci_ctfm will equal ci_master_key->mk_ctfm.
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
index 058e2e0fda430..148a54fb556a6 100644
--- a/fs/crypto/keyinfo.c
+++ b/fs/crypto/keyinfo.c
@@ -542,6 +542,8 @@ int fscrypt_get_encryption_info(struct inode *inode)
 	if (!crypt_info)
 		return -ENOMEM;
 
+	crypt_info->ci_inode = inode;
+
 	crypt_info->ci_flags = ctx.flags;
 	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
 	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
-- 
2.21.0