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[RFC,10/17] fscrypt: let fscrypt_infos be owned by an extent

Message ID e5e72a4404601c495551ea96f80f0eca4bc8942c.1672547582.git.sweettea-kernel@dorminy.me (mailing list archive)
State New, archived
Headers show
Series fscrypt: add per-extent encryption keys | expand

Commit Message

Sweet Tea Dorminy Jan. 1, 2023, 5:06 a.m. UTC
In order to notify extents when their info is part of a master key which
is going away, the fscrypt_info must have a backpointer to the extent
somehow. Similarly, if a fscrypt_info is owned by an extent, the info
must not have a pointer to an inode -- multiple inodes may reference a
extent, and the first inode to cause an extent's creation may have a
lifetime much shorter than the extent, so there is no inode pointer
safe to track in an extent-owned info. Therefore, this adds a new
pointer for extent-owned infos to track their extent and updates
fscrypt_setup_encryption_info() accordingly.

 Since it's simple to track the piece of extent memory pointing to the
info, and for the extent to then go from such a pointer to the whole
extent via container_of(), we store that. Although some sort of generic
void * or some artificial fscrypt_extent embedded structure would also
work, those would require additional plumbing which doesn't seem
strictly required or clarifying.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
 fs/crypto/fscrypt_private.h | 6 ++++++
 fs/crypto/keysetup.c        | 6 +++++-
 2 files changed, 11 insertions(+), 1 deletion(-)
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Patch

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 0c7b785f1d8c..dc45cd35391f 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -229,6 +229,12 @@  struct fscrypt_info {
 	/* Back-pointer to the inode, for infos owned by a specific inode */
 	struct inode *ci_inode;
 
+	/*
+	 * Back-pointer to the info pointer in the extent, for infos owned
+	 * by an extent
+	 */
+	struct fscrypt_info **ci_info_ptr;
+
 	/* The superblock of the filesystem to which this fscrypt_info pertains */
 	struct super_block *ci_sb;
 
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 04f01da900ca..c611e2613aa6 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -567,7 +567,11 @@  fscrypt_setup_encryption_info(struct inode *inode,
 	if (!crypt_info)
 		return -ENOMEM;
 
-	crypt_info->ci_inode = inode;
+	if (fscrypt_uses_extent_encryption(inode))
+		crypt_info->ci_info_ptr = info_ptr;
+	else
+		crypt_info->ci_inode = inode;
+
 	crypt_info->ci_sb = inode->i_sb;
 	crypt_info->ci_policy = *policy;
 	memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE);