Commit 983c7db3 authored by Milan Broz's avatar Milan Broz Committed by Alasdair G Kergon
Browse files

dm crypt: always disable discard_zeroes_data 



If optional discard support in dm-crypt is enabled, discards requests
bypass the crypt queue and blocks of the underlying device are discarded.
For the read path, discarded blocks are handled the same as normal
ciphertext blocks, thus decrypted.

So if the underlying device announces discarded regions return zeroes,
dm-crypt must disable this flag because after decryption there is just
random noise instead of zeroes.

Signed-off-by: default avatarMilan Broz <mbroz@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 82324809

drivers/md/dm-crypt.c

+2 −0
Original line number Original line Diff line number Diff line
@@ -1698,6 +1698,8 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv) 
	}

	}





	ti->num_flush_requests = 1;

	ti->num_flush_requests = 1;

	ti->discard_zeroes_data_unsupported = 1;



	return 0;

	return 0;





bad:

bad:

drivers/md/dm-table.c

+19 −0
Original line number Original line Diff line number Diff line
@@ -1283,6 +1283,22 @@ static bool dm_table_supports_flush(struct dm_table *t, unsigned flush) 
	return 0;

	return 0;

}

}





static bool dm_table_discard_zeroes_data(struct dm_table *t)

{

	struct dm_target *ti;

	unsigned i = 0;



	/* Ensure that all targets supports discard_zeroes_data. */

	while (i < dm_table_get_num_targets(t)) {

		ti = dm_table_get_target(t, i++);



		if (ti->discard_zeroes_data_unsupported)

			return 0;

	}



	return 1;

}



void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,

void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,

			       struct queue_limits *limits)

			       struct queue_limits *limits)

{

{
@@ -1305,6 +1321,9 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q, 
	}

	}

	blk_queue_flush(q, flush);

	blk_queue_flush(q, flush);





	if (!dm_table_discard_zeroes_data(t))

		q->limits.discard_zeroes_data = 0;



	dm_table_set_integrity(t);

	dm_table_set_integrity(t);





	/*

	/*

include/linux/device-mapper.h

+5 −0
Original line number Original line Diff line number Diff line
@@ -197,6 +197,11 @@ struct dm_target { 
	 * whether or not its underlying devices have support.

	 * whether or not its underlying devices have support.

	 */

	 */

	unsigned discards_supported:1;

	unsigned discards_supported:1;



	/*

	 * Set if this target does not return zeroes on discarded blocks.

	 */

	unsigned discard_zeroes_data_unsupported:1;

};

};





/* Each target can link one of these into the table */

/* Each target can link one of these into the table */

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