dm crypt: use shifts instead of sector_div

sector_div is very slow, so we introduce a variable sector_shift and
use shift instead of sector_div.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-crypt.c

@@ -172,7 +172,8 @@ struct crypt_config {
 	} iv_gen_private;
 	sector_t iv_offset;
 	unsigned int iv_size;
-	unsigned int sector_size;
+	unsigned short int sector_size;
+	unsigned char sector_shift;
 
 	/* ESSIV: struct crypto_cipher *essiv_tfm */
 	void *iv_private;
@@ -1062,7 +1063,7 @@ static int crypt_convert_block_aead(struct crypt_config *cc,
 	dmreq = dmreq_of_req(cc, req);
 	dmreq->iv_sector = ctx->cc_sector;
 	if (test_bit(CRYPT_IV_LARGE_SECTORS, &cc->cipher_flags))
-		sector_div(dmreq->iv_sector, cc->sector_size >> SECTOR_SHIFT);
+		dmreq->iv_sector >>= cc->sector_shift;
 	dmreq->ctx = ctx;
 
 	*org_tag_of_dmreq(cc, dmreq) = tag_offset;
@@ -1155,7 +1156,7 @@ static int crypt_convert_block_skcipher(struct crypt_config *cc,
 	dmreq = dmreq_of_req(cc, req);
 	dmreq->iv_sector = ctx->cc_sector;
 	if (test_bit(CRYPT_IV_LARGE_SECTORS, &cc->cipher_flags))
-		sector_div(dmreq->iv_sector, cc->sector_size >> SECTOR_SHIFT);
+		dmreq->iv_sector >>= cc->sector_shift;
 	dmreq->ctx = ctx;
 
 	*org_tag_of_dmreq(cc, dmreq) = tag_offset;
@@ -1290,7 +1291,7 @@ static int crypt_convert(struct crypt_config *cc,
 			 struct convert_context *ctx)
 {
 	unsigned int tag_offset = 0;
-	unsigned int sector_step = cc->sector_size / (1 << SECTOR_SHIFT);
+	unsigned int sector_step = cc->sector_size >> SECTOR_SHIFT;
 	int r;
 
 	atomic_set(&ctx->cc_pending, 1);
@@ -2575,13 +2576,14 @@ static int crypt_ctr_optional(struct dm_target *ti, unsigned int argc, char **ar
 			cc->cipher_auth = kstrdup(sval, GFP_KERNEL);
 			if (!cc->cipher_auth)
 				return -ENOMEM;
-		} else if (sscanf(opt_string, "sector_size:%u%c", &cc->sector_size, &dummy) == 1) {
+		} else if (sscanf(opt_string, "sector_size:%hu%c", &cc->sector_size, &dummy) == 1) {
 			if (cc->sector_size < (1 << SECTOR_SHIFT) ||
 			    cc->sector_size > 4096 ||
-			    (1 << ilog2(cc->sector_size) != cc->sector_size)) {
+			    (cc->sector_size & (cc->sector_size - 1))) {
 				ti->error = "Invalid feature value for sector_size";
 				return -EINVAL;
 			}
+			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 {
@@ -2625,6 +2627,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	}
 	cc->key_size = key_size;
 	cc->sector_size = (1 << SECTOR_SHIFT);
+	cc->sector_shift = 0;
 
 	ti->private = cc;
 
@@ -2870,7 +2873,7 @@ static void crypt_status(struct dm_target *ti, status_type_t type,
 		num_feature_args += !!ti->num_discard_bios;
 		num_feature_args += test_bit(DM_CRYPT_SAME_CPU, &cc->flags);
 		num_feature_args += test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags);
-		num_feature_args += (cc->sector_size != (1 << SECTOR_SHIFT)) ? 1 : 0;
+		num_feature_args += cc->sector_size != (1 << SECTOR_SHIFT);
 		num_feature_args += test_bit(CRYPT_IV_LARGE_SECTORS, &cc->cipher_flags);
 		if (cc->on_disk_tag_size)
 			num_feature_args++;