From: Michael Halcrow Subject: [RFC PATCH 2/4] dm-crypt: Skip encryption of file system-encrypted blocks Date: Wed, 14 Jun 2017 16:40:38 -0700 Message-ID: <20170614234040.4326-3-mhalcrow@google.com> References: <20170614234040.4326-1-mhalcrow@google.com> To: Michael Halcrow , "Theodore Y . Ts'o" , Eric Biggers , Jaegeuk Kim , linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, dm-devel@redhat.com, linux-ext4@vger.kernel.org, Tyler Hicks Return-path: In-Reply-To: <20170614234040.4326-1-mhalcrow@google.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org 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 --- 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