ecryptfs: improved dependency checking and reporting

So, I compiled a 2.6.31-rc5 kernel with ecryptfs and loaded its module.
When it came time to mount my filesystem, I got this in dmesg, and it
refused to mount:

[93577.776637] Unable to allocate crypto cipher with name [aes]; rc = [-2]
[93577.783280] Error attempting to initialize key TFM cipher with name = [aes]; rc = [-2]
[93577.791183] Error attempting to initialize cipher with name = [aes] and key size = [32]; rc = [-2]
[93577.800113] Error parsing options; rc = [-22]

I figured from the error message that I'd either forgotten to load "aes"
or that my key size was bogus.  Neither one of those was the case.  In
fact, I was missing the CRYPTO_ECB config option and the 'ecb' module.
Unfortunately, there's no trace of 'ecb' in that error message.

I've done two things to fix this.  First, I've modified ecryptfs's
Kconfig entry to select CRYPTO_ECB and CRYPTO_CBC.  I also took CRYPTO
out of the dependencies since the 'select' will take care of it for us.

I've also modified the error messages to print a string that should
contain both 'ecb' and 'aes' in my error case.  That will give any
future users a chance of finding the right modules and Kconfig options.

I also wonder if we should:

	select CRYPTO_AES if !EMBEDDED

since I think most ecryptfs users are using AES like me.

Cc: ecryptfs-devel@lists.launchpad.net
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Dustin Kirkland <kirkland@canonical.com>
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
[tyhicks@linux.vnet.ibm.com: Removed extra newline, 80-char violation]
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

fs/ecryptfs/Kconfig

@@ -1,6 +1,8 @@
 config ECRYPT_FS
 	tristate "eCrypt filesystem layer support (EXPERIMENTAL)"
-	depends on EXPERIMENTAL && KEYS && CRYPTO && NET
+	depends on EXPERIMENTAL && KEYS && NET
+	select CRYPTO_ECB
+	select CRYPTO_CBC
 	help
 	  Encrypted filesystem that operates on the VFS layer.  See
 	  <file:Documentation/filesystems/ecryptfs.txt> to learn more about

fs/ecryptfs/crypto.c

@@ -1763,7 +1763,7 @@ ecryptfs_process_key_cipher(struct crypto_blkcipher **key_tfm,
 	if (IS_ERR(*key_tfm)) {
 		rc = PTR_ERR(*key_tfm);
 		printk(KERN_ERR "Unable to allocate crypto cipher with name "
-		       "[%s]; rc = [%d]\n", cipher_name, rc);
+		       "[%s]; rc = [%d]\n", full_alg_name, rc);
 		goto out;
 	}
 	crypto_blkcipher_set_flags(*key_tfm, CRYPTO_TFM_REQ_WEAK_KEY);
@@ -1776,7 +1776,8 @@ ecryptfs_process_key_cipher(struct crypto_blkcipher **key_tfm,
 	rc = crypto_blkcipher_setkey(*key_tfm, dummy_key, *key_size);
 	if (rc) {
 		printk(KERN_ERR "Error attempting to set key of size [%zd] for "
-		       "cipher [%s]; rc = [%d]\n", *key_size, cipher_name, rc);
+		       "cipher [%s]; rc = [%d]\n", *key_size, full_alg_name,
+		       rc);
 		rc = -EINVAL;
 		goto out;
 	}