Commit 787f1b28 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm-verity, dm-crypt: align "struct bvec_iter" correctly 

"struct bvec_iter" is defined with the __packed attribute, so it is
aligned on a single byte. On X86 (and on other architectures that support
unaligned addresses in hardware), "struct bvec_iter" is accessed using the
8-byte and 4-byte memory instructions, however these instructions are less
efficient if they operate on unaligned addresses.

(on RISC machines that don't have unaligned access in hardware, GCC
generates byte-by-byte accesses that are very inefficient - see [1])

This commit reorders the entries in "struct dm_verity_io" and "struct
convert_context", so that "struct bvec_iter" is aligned on 8 bytes.

[1] https://lore.kernel.org/all/ZcLuWUNRZadJr0tQ@fedora/T/



Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent 42e15d12

drivers/md/dm-crypt.c

+2 −2
Original line number Diff line number Diff line
@@ -53,11 +53,11 @@ 
struct convert_context {

	struct completion restart;

	struct bio *bio_in;

	struct bio *bio_out;

	struct bvec_iter iter_in;

	struct bio *bio_out;

	struct bvec_iter iter_out;

	u64 cc_sector;

	atomic_t cc_pending;

	u64 cc_sector;

	union {

		struct skcipher_request *req;

		struct aead_request *req_aead;

drivers/md/dm-verity.h

+2 −2
Original line number Diff line number Diff line
@@ -80,12 +80,12 @@ struct dm_verity_io { 
	/* original value of bio->bi_end_io */

	bio_end_io_t *orig_bi_end_io;



	struct bvec_iter iter;



	sector_t block;

	unsigned int n_blocks;

	bool in_tasklet;



	struct bvec_iter iter;



	struct work_struct work;



	char *recheck_buffer;