File systems can encrypt some of their data blocks with their own
encryption keys, and for those blocks another round of encryption at
the dm-crypt layer may be redundant, depending on the keys being used.
This patch enables dm-crypt to observe the REQ_NOENCRYPT flag as an
indicator that a bio request should bypass the dm-crypt encryption
queue.
By default dm-crypt will ignore this request flag from the file
system. The user must set the allow_encrypt_override option to enable
this functionality. Once the dm-crypt has been used with the
allow_encrypt_override option for any given block device, it must
continue to be used with the option to avoid the possibility of data
corruption.
Signed-off-by: Michael Halcrow <mhalcrow@xxxxxxxxxx>
---
drivers/md/dm-crypt.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index ebf9e72d479b..14ca8a6de3d9 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -125,7 +125,8 @@ struct iv_tcw_private {
* and encrypts / decrypts at the same time.
*/
enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID,
- DM_CRYPT_SAME_CPU, DM_CRYPT_NO_OFFLOAD };
+ DM_CRYPT_SAME_CPU, DM_CRYPT_NO_OFFLOAD,
+ DM_CRYPT_ENCRYPT_OVERRIDE };
enum cipher_flags {
CRYPT_MODE_INTEGRITY_AEAD, /* Use authenticated mode for cihper */
@@ -2572,6 +2573,8 @@ static int crypt_ctr_optional(struct dm_target *ti, unsigned int argc, char **ar
cc->sector_shift = __ffs(cc->sector_size) - SECTOR_SHIFT;
} else if (!strcasecmp(opt_string, "iv_large_sectors"))
set_bit(CRYPT_IV_LARGE_SECTORS, &cc->cipher_flags);
+ else if (!strcasecmp(opt_string, "allow_encrypt_override"))
+ set_bit(DM_CRYPT_ENCRYPT_OVERRIDE, &cc->flags);
else {
ti->error = "Invalid feature arguments";
return -EINVAL;
@@ -2770,12 +2773,15 @@ static int crypt_map(struct dm_target *ti, struct bio *bio)
struct crypt_config *cc = ti->private;
/*
- * If bio is REQ_PREFLUSH or REQ_OP_DISCARD, just bypass crypt queues.
+ * If bio is REQ_PREFLUSH, REQ_NOENCRYPT, or REQ_OP_DISCARD,
+ * just bypass crypt queues.
* - for REQ_PREFLUSH device-mapper core ensures that no IO is in-flight
* - for REQ_OP_DISCARD caller must use flush if IO ordering matters
*/
- if (unlikely(bio->bi_opf & REQ_PREFLUSH ||
- bio_op(bio) == REQ_OP_DISCARD)) {
+ if (unlikely(bio->bi_opf & REQ_PREFLUSH) ||
+ (unlikely(bio->bi_opf & REQ_NOENCRYPT) &&
+ test_bit(DM_CRYPT_ENCRYPT_OVERRIDE, &cc->flags)) ||
+ bio_op(bio) == REQ_OP_DISCARD) {
bio->bi_bdev = cc->dev->bdev;
if (bio_sectors(bio))
bio->bi_iter.bi_sector = cc->start +
@@ -2862,6 +2868,7 @@ static void crypt_status(struct dm_target *ti, status_type_t type,
num_feature_args += test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags);
num_feature_args += cc->sector_size != (1 << SECTOR_SHIFT);
num_feature_args += test_bit(CRYPT_IV_LARGE_SECTORS, &cc->cipher_flags);
+ num_feature_args += test_bit(DM_CRYPT_ENCRYPT_OVERRIDE, &cc->flags);
if (cc->on_disk_tag_size)
num_feature_args++;
if (num_feature_args) {
@@ -2878,6 +2885,8 @@ static void crypt_status(struct dm_target *ti, status_type_t type,
DMEMIT(" sector_size:%d", cc->sector_size);
if (test_bit(CRYPT_IV_LARGE_SECTORS, &cc->cipher_flags))
DMEMIT(" iv_large_sectors");
+ if (test_bit(DM_CRYPT_ENCRYPT_OVERRIDE, &cc->flags))
+ DMEMIT(" allow_encrypt_override");
}
break;
--
2.13.1.508.gb3defc5cc-goog
