ext4 crypto: use per-inode tfm structure

As suggested by Herbert Xu, we shouldn't allocate a new tfm each time
we read or write a page.  Instead we can use a single tfm hanging off
the inode's crypt_info structure for all of our encryption needs for
that inode, since the tfm can be used by multiple crypto requests in
parallel.

Also use cmpxchg() to avoid races that could result in crypt_info
structure getting doubly allocated or doubly freed.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 1 insertions, 47 deletions

diff --git a/fs/ext4/crypto_fname.c b/fs/ext4/crypto_fname.c
index e63dd29..29a2dc9 100644
--- a/fs/ext4/crypto_fname.c
+++ b/fs/ext4/crypto_fname.c
@@ -252,52 +252,6 @@ static int digest_decode(const char *src, int len, char *dst)
 	return cp - dst;
 }
 
-int ext4_setup_fname_crypto(struct inode *inode)
-{
-	struct ext4_inode_info *ei = EXT4_I(inode);
-	struct ext4_crypt_info *ci = ei->i_crypt_info;
-	struct crypto_ablkcipher *ctfm;
-	int res;
-
-	/* Check if the crypto policy is set on the inode */
-	res = ext4_encrypted_inode(inode);
-	if (res == 0)
-		return 0;
-
-	res = ext4_get_encryption_info(inode);
-	if (res < 0)
-		return res;
-	ci = ei->i_crypt_info;
-
-	if (!ci || ci->ci_ctfm)
-		return 0;
-
-	if (ci->ci_filename_mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
-		printk_once(KERN_WARNING "ext4: unsupported key mode %d\n",
-			    ci->ci_filename_mode);
-		return -ENOKEY;
-	}
-
-	ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))", 0, 0);
-	if (!ctfm || IS_ERR(ctfm)) {
-		res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
-		printk(KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
-		       __func__, res);
-		return res;
-	}
-	crypto_ablkcipher_clear_flags(ctfm, ~0);
-	crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
-			     CRYPTO_TFM_REQ_WEAK_KEY);
-
-	res = crypto_ablkcipher_setkey(ctfm, ci->ci_raw, ci->ci_size);
-	if (res) {
-		crypto_free_ablkcipher(ctfm);
-		return -EIO;
-	}
-	ci->ci_ctfm = ctfm;
-	return 0;
-}
-
 /**
  * ext4_fname_crypto_round_up() -
  *
@@ -449,7 +403,7 @@ int ext4_fname_setup_filename(struct inode *dir, const struct qstr *iname,
 		fname->disk_name.len = iname->len;
 		goto out;
 	}
-	ret = ext4_setup_fname_crypto(dir);
+	ret = ext4_get_encryption_info(dir);
 	if (ret)
 		return ret;
 	ci = EXT4_I(dir)->i_crypt_info;