dm log: fix create_log_context to use logical_block_size of log device

create_log_context() must use the logical_block_size from the log disk,
where the I/O happens, not the target's logical_block_size.

Signed-off-by: Mike Snitzer <[e-mail]>
Signed-off-by: Alasdair G Kergon <[e-mail]>

drivers/md/dm-log.c

···
 		/*
 		 * Buffer holds both header and bitset.
 		 */
-		buf_size = dm_round_up((LOG_OFFSET << SECTOR_SHIFT) +
-				       bitset_size,
-				       ti->limits.logical_block_size);
+		buf_size =
+		    dm_round_up((LOG_OFFSET << SECTOR_SHIFT) + bitset_size,
+				bdev_logical_block_size(lc->header_location.
+							    bdev));
 
 		if (buf_size > i_size_read(dev->bdev->bd_inode)) {
 			DMWARN("log device %s too small: need %llu bytes",