Btrfs: check_int: use the known block location

The xfstest btrfs/014 which tests the balance operation caused issues with
the check_int module. The attempt was made to use btrfs_map_block() to
find the physical location for a written block. However, this was not
at all needed since the location of the written block was known since
a hook to submit_bio() was the reason for entering the check_int module.
Additionally, after a block relocation it happened that btrfs_map_block()
failed causing misleading error messages afterwards.

This patch changes the check_int module to use the known information of
the physical location from the bio.

Reported-by: Wang Shilong <wangshilong1991@gmail.com>
Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Tested-by: Wang Shilong <wangshilong1991@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/check-integrity.c

@@ -326,9 +326,6 @@ static int btrfsic_handle_extent_data(struct btrfsic_state *state,
 static int btrfsic_map_block(struct btrfsic_state *state, u64 bytenr, u32 len,
 			     struct btrfsic_block_data_ctx *block_ctx_out,
 			     int mirror_num);
-static int btrfsic_map_superblock(struct btrfsic_state *state, u64 bytenr,
-				  u32 len, struct block_device *bdev,
-				  struct btrfsic_block_data_ctx *block_ctx_out);
 static void btrfsic_release_block_ctx(struct btrfsic_block_data_ctx *block_ctx);
 static int btrfsic_read_block(struct btrfsic_state *state,
 			      struct btrfsic_block_data_ctx *block_ctx);
@@ -1607,25 +1604,6 @@ static int btrfsic_map_block(struct btrfsic_state *state, u64 bytenr, u32 len,
 	return ret;
 }
 
-static int btrfsic_map_superblock(struct btrfsic_state *state, u64 bytenr,
-				  u32 len, struct block_device *bdev,
-				  struct btrfsic_block_data_ctx *block_ctx_out)
-{
-	block_ctx_out->dev = btrfsic_dev_state_lookup(bdev);
-	block_ctx_out->dev_bytenr = bytenr;
-	block_ctx_out->start = bytenr;
-	block_ctx_out->len = len;
-	block_ctx_out->datav = NULL;
-	block_ctx_out->pagev = NULL;
-	block_ctx_out->mem_to_free = NULL;
-	if (NULL != block_ctx_out->dev) {
-		return 0;
-	} else {
-		printk(KERN_INFO "btrfsic: error, cannot lookup dev (#2)!\n");
-		return -ENXIO;
-	}
-}
-
 static void btrfsic_release_block_ctx(struct btrfsic_block_data_ctx *block_ctx)
 {
 	if (block_ctx->mem_to_free) {
@@ -2002,24 +1980,13 @@ again:
 			}
 		}
 
-		if (block->is_superblock)
-			ret = btrfsic_map_superblock(state, bytenr,
-						     processed_len,
-						     bdev, &block_ctx);
-		else
-			ret = btrfsic_map_block(state, bytenr, processed_len,
-						&block_ctx, 0);
-		if (ret) {
-			printk(KERN_INFO
-			       "btrfsic: btrfsic_map_block(root @%llu)"
-			       " failed!\n", bytenr);
-			goto continue_loop;
-		}
-		block_ctx.datav = mapped_datav;
-		/* the following is required in case of writes to mirrors,
-		 * use the same that was used for the lookup */
 		block_ctx.dev = dev_state;
 		block_ctx.dev_bytenr = dev_bytenr;
+		block_ctx.start = bytenr;
+		block_ctx.len = processed_len;
+		block_ctx.pagev = NULL;
+		block_ctx.mem_to_free = NULL;
+		block_ctx.datav = mapped_datav;
 
 		if (is_metadata || state->include_extent_data) {
 			block->never_written = 0;
@@ -2133,10 +2100,6 @@ again:
 			/* this is getting ugly for the
 			 * include_extent_data case... */
 			bytenr = 0;	/* unknown */
-			block_ctx.start = bytenr;
-			block_ctx.len = processed_len;
-			block_ctx.mem_to_free = NULL;
-			block_ctx.pagev = NULL;
 		} else {
 			processed_len = state->metablock_size;
 			bytenr = btrfs_stack_header_bytenr(
@@ -2149,22 +2112,15 @@ again:
 				       "Written block @%llu (%s/%llu/?)"
 				       " !found in hash table, M.\n",
 				       bytenr, dev_state->name, dev_bytenr);
-
-			ret = btrfsic_map_block(state, bytenr, processed_len,
-						&block_ctx, 0);
-			if (ret) {
-				printk(KERN_INFO
-				       "btrfsic: btrfsic_map_block(root @%llu)"
-				       " failed!\n",
-				       dev_bytenr);
-				goto continue_loop;
-			}
 		}
-		block_ctx.datav = mapped_datav;
+
-		/* the following is required in case of writes to mirrors,
-		 * use the same that was used for the lookup */
 		block_ctx.dev = dev_state;
 		block_ctx.dev_bytenr = dev_bytenr;
+		block_ctx.start = bytenr;
+		block_ctx.len = processed_len;
+		block_ctx.pagev = NULL;
+		block_ctx.mem_to_free = NULL;
+		block_ctx.datav = mapped_datav;
 
 		block = btrfsic_block_alloc();
 		if (NULL == block) {