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Commit 364c6230 authored by Shivaprasad Hongal's avatar Shivaprasad Hongal Committed by Gerrit - the friendly Code Review server
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[ANDROID] dm-crypt: Skip encryption of file system-encrypted blocks 



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.

Change-Id: Ie1b4d40f4e4d96f3349ec8970c56230b2de2de1a
Signed-off-by: default avatarMichael Halcrow <mhalcrow@google.com>
Git-repo: https://android.googlesource.com/kernel/common/


[shongal@codeaurora.org: resolved trivial merge conflicts]
Signed-off-by: default avatarShivaprasad Hongal <shongal@codeaurora.org>
parent 155804e9

drivers/md/dm-crypt.c

+14 −4
Original line number Diff line number Diff line
@@ -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 */
@@ -2653,6 +2654,8 @@ 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;
@@ -2862,12 +2865,15 @@ 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_set_dev(bio, cc->dev->bdev);

		if (bio_sectors(bio))

			bio->bi_iter.bi_sector = cc->start +
@@ -2954,6 +2960,8 @@ 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) {
@@ -2970,6 +2978,8 @@ 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;