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SubjectRe: [PATCH] eCryptfs: Load each file decryption key only once
On Fri, Dec 21, 2007 at 08:05:30PM -0600, Trevor Highland wrote:
> eCryptfs: Load each file decryption key only once
>
> There is no need to keep re-setting the same key for any given
> eCryptfs inode. This patch optimizes the use of the crypto API and
> helps performance a bit.

There is no reason for the crypt_stat->key value for any given
eCryptfs inode to change during the life of the inode, and each
crypt_stat gets its own crypto transform, so I do not see a problem
with Trevor's suggestion. It will save unnecessary calls to
crypto_blkcipher_setkey(), and I expect it will speed things up a
little.

I include an updated patch against 2.6.24-rc7.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
---
fs/ecryptfs/crypto.c | 40 ++++++++++++++++++++++------------------
fs/ecryptfs/ecryptfs_kernel.h | 1 +
2 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index f8ef0af..40849cf 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -353,16 +353,18 @@ static int encrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
ecryptfs_dump_hex(crypt_stat->key,
crypt_stat->key_size);
}
- /* Consider doing this once, when the file is opened */
mutex_lock(&crypt_stat->cs_tfm_mutex);
- rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
- crypt_stat->key_size);
- if (rc) {
- ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
- rc);
- mutex_unlock(&crypt_stat->cs_tfm_mutex);
- rc = -EINVAL;
- goto out;
+ if (!(crypt_stat->flags & ECRYPTFS_TFM_KEY_SET)) {
+ rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
+ crypt_stat->key_size);
+ if (rc) {
+ printk(KERN_ERR "%s: Error setting key; rc = [%d]\n",
+ __FUNCTION__, rc);
+ mutex_unlock(&crypt_stat->cs_tfm_mutex);
+ rc = -EINVAL;
+ goto out;
+ }
+ crypt_stat->flags |= ECRYPTFS_TFM_KEY_SET;
}
ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes.\n", size);
crypto_blkcipher_encrypt_iv(&desc, dest_sg, src_sg, size);
@@ -685,16 +687,18 @@ static int decrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
};
int rc = 0;

- /* Consider doing this once, when the file is opened */
mutex_lock(&crypt_stat->cs_tfm_mutex);
- rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
- crypt_stat->key_size);
- if (rc) {
- ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
- rc);
- mutex_unlock(&crypt_stat->cs_tfm_mutex);
- rc = -EINVAL;
- goto out;
+ if (!(crypt_stat->flags & ECRYPTFS_TFM_KEY_SET)) {
+ rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
+ crypt_stat->key_size);
+ if (rc) {
+ printk(KERN_ERR "%s: Error setting key; rc = [%d]\n",
+ __FUNCTION__, rc);
+ mutex_unlock(&crypt_stat->cs_tfm_mutex);
+ rc = -EINVAL;
+ goto out;
+ }
+ crypt_stat->flags |= ECRYPTFS_TFM_KEY_SET;
}
ecryptfs_printk(KERN_DEBUG, "Decrypting [%d] bytes.\n", size);
rc = crypto_blkcipher_decrypt_iv(&desc, dest_sg, src_sg, size);
diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index ce7a5d4..2abb110 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -234,6 +234,7 @@ struct ecryptfs_crypt_stat {
#define ECRYPTFS_KEY_VALID 0x00000080
#define ECRYPTFS_METADATA_IN_XATTR 0x00000100
#define ECRYPTFS_VIEW_AS_ENCRYPTED 0x00000200
+#define ECRYPTFS_TFM_KEY_SET 0x00000400
u32 flags;
unsigned int file_version;
size_t iv_bytes;
--
1.5.0.6


> Signed-off-by: Trevor Highland <trevor.highland@gmail.com>
> ---
> fs/ecryptfs/crypto.c | 9 +++++----
> 1 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
> index 70f7aab..949fe44 100644
> --- a/fs/ecryptfs/crypto.c
> +++ b/fs/ecryptfs/crypto.c
> @@ -353,7 +353,6 @@ static int encrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
> ecryptfs_dump_hex(crypt_stat->key,
> crypt_stat->key_size);
> }
> - /* Consider doing this once, when the file is opened */
> mutex_lock(&crypt_stat->cs_tfm_mutex);
> if (!(crypt_stat->flags & ECRYPTFS_KEY_SET)) {
> rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
> @@ -687,10 +686,12 @@ static int decrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
> };
> int rc = 0;
>
> - /* Consider doing this once, when the file is opened */
> mutex_lock(&crypt_stat->cs_tfm_mutex);
> - rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
> - crypt_stat->key_size);
> + if (!(crypt_stat->flags & ECRYPTFS_KEY_SET)) {
> + rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
> + crypt_stat->key_size);
> + crypt_stat->flags |= ECRYPTFS_KEY_SET;
> + }
> if (rc) {
> ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
> rc);


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