Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2913 insertions, 0 deletions

diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
new file mode 100644
index 000000000..81a8c87a5
--- /dev/null
+++ b/fs/btrfs/check-integrity.c
@@ -0,0 +1,2913 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) STRATO AG 2011.  All rights reserved.
+ */
+
+/*
+ * This module can be used to catch cases when the btrfs kernel
+ * code executes write requests to the disk that bring the file
+ * system in an inconsistent state. In such a state, a power-loss
+ * or kernel panic event would cause that the data on disk is
+ * lost or at least damaged.
+ *
+ * Code is added that examines all block write requests during
+ * runtime (including writes of the super block). Three rules
+ * are verified and an error is printed on violation of the
+ * rules:
+ * 1. It is not allowed to write a disk block which is
+ *    currently referenced by the super block (either directly
+ *    or indirectly).
+ * 2. When a super block is written, it is verified that all
+ *    referenced (directly or indirectly) blocks fulfill the
+ *    following requirements:
+ *    2a. All referenced blocks have either been present when
+ *        the file system was mounted, (i.e., they have been
+ *        referenced by the super block) or they have been
+ *        written since then and the write completion callback
+ *        was called and no write error was indicated and a
+ *        FLUSH request to the device where these blocks are
+ *        located was received and completed.
+ *    2b. All referenced blocks need to have a generation
+ *        number which is equal to the parent's number.
+ *
+ * One issue that was found using this module was that the log
+ * tree on disk became temporarily corrupted because disk blocks
+ * that had been in use for the log tree had been freed and
+ * reused too early, while being referenced by the written super
+ * block.
+ *
+ * The search term in the kernel log that can be used to filter
+ * on the existence of detected integrity issues is
+ * "btrfs: attempt".
+ *
+ * The integrity check is enabled via mount options. These
+ * mount options are only supported if the integrity check
+ * tool is compiled by defining BTRFS_FS_CHECK_INTEGRITY.
+ *
+ * Example #1, apply integrity checks to all metadata:
+ * mount /dev/sdb1 /mnt -o check_int
+ *
+ * Example #2, apply integrity checks to all metadata and
+ * to data extents:
+ * mount /dev/sdb1 /mnt -o check_int_data
+ *
+ * Example #3, apply integrity checks to all metadata and dump
+ * the tree that the super block references to kernel messages
+ * each time after a super block was written:
+ * mount /dev/sdb1 /mnt -o check_int,check_int_print_mask=263
+ *
+ * If the integrity check tool is included and activated in
+ * the mount options, plenty of kernel memory is used, and
+ * plenty of additional CPU cycles are spent. Enabling this
+ * functionality is not intended for normal use. In most
+ * cases, unless you are a btrfs developer who needs to verify
+ * the integrity of (super)-block write requests, do not
+ * enable the config option BTRFS_FS_CHECK_INTEGRITY to
+ * include and compile the integrity check tool.
+ *
+ * Expect millions of lines of information in the kernel log with an
+ * enabled check_int_print_mask. Therefore set LOG_BUF_SHIFT in the
+ * kernel config to at least 26 (which is 64MB). Usually the value is
+ * limited to 21 (which is 2MB) in init/Kconfig. The file needs to be
+ * changed like this before LOG_BUF_SHIFT can be set to a high value:
+ * config LOG_BUF_SHIFT
+ *       int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
+ *       range 12 30
+ */
+
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <linux/genhd.h>
+#include <linux/blkdev.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <crypto/hash.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "extent_io.h"
+#include "volumes.h"
+#include "print-tree.h"
+#include "locking.h"
+#include "check-integrity.h"
+#include "rcu-string.h"
+#include "compression.h"
+
+#define BTRFSIC_BLOCK_HASHTABLE_SIZE 0x10000
+#define BTRFSIC_BLOCK_LINK_HASHTABLE_SIZE 0x10000
+#define BTRFSIC_DEV2STATE_HASHTABLE_SIZE 0x100
+#define BTRFSIC_BLOCK_MAGIC_NUMBER 0x14491051
+#define BTRFSIC_BLOCK_LINK_MAGIC_NUMBER 0x11070807
+#define BTRFSIC_DEV2STATE_MAGIC_NUMBER 0x20111530
+#define BTRFSIC_BLOCK_STACK_FRAME_MAGIC_NUMBER 20111300
+#define BTRFSIC_TREE_DUMP_MAX_INDENT_LEVEL (200 - 6)	/* in characters,
+							 * excluding " [...]" */
+#define BTRFSIC_GENERATION_UNKNOWN ((u64)-1)
+
+/*
+ * The definition of the bitmask fields for the print_mask.
+ * They are specified with the mount option check_integrity_print_mask.
+ */
+#define BTRFSIC_PRINT_MASK_SUPERBLOCK_WRITE			0x00000001
+#define BTRFSIC_PRINT_MASK_ROOT_CHUNK_LOG_TREE_LOCATION		0x00000002
+#define BTRFSIC_PRINT_MASK_TREE_AFTER_SB_WRITE			0x00000004
+#define BTRFSIC_PRINT_MASK_TREE_BEFORE_SB_WRITE			0x00000008
+#define BTRFSIC_PRINT_MASK_SUBMIT_BIO_BH			0x00000010
+#define BTRFSIC_PRINT_MASK_END_IO_BIO_BH			0x00000020
+#define BTRFSIC_PRINT_MASK_VERBOSE				0x00000040
+#define BTRFSIC_PRINT_MASK_VERY_VERBOSE				0x00000080
+#define BTRFSIC_PRINT_MASK_INITIAL_TREE				0x00000100
+#define BTRFSIC_PRINT_MASK_INITIAL_ALL_TREES			0x00000200
+#define BTRFSIC_PRINT_MASK_INITIAL_DATABASE			0x00000400
+#define BTRFSIC_PRINT_MASK_NUM_COPIES				0x00000800
+#define BTRFSIC_PRINT_MASK_TREE_WITH_ALL_MIRRORS		0x00001000
+#define BTRFSIC_PRINT_MASK_SUBMIT_BIO_BH_VERBOSE		0x00002000
+
+struct btrfsic_dev_state;
+struct btrfsic_state;
+
+struct btrfsic_block {
+	u32 magic_num;		/* only used for debug purposes */
+	unsigned int is_metadata:1;	/* if it is meta-data, not data-data */
+	unsigned int is_superblock:1;	/* if it is one of the superblocks */
+	unsigned int is_iodone:1;	/* if is done by lower subsystem */
+	unsigned int iodone_w_error:1;	/* error was indicated to endio */
+	unsigned int never_written:1;	/* block was added because it was
+					 * referenced, not because it was
+					 * written */
+	unsigned int mirror_num;	/* large enough to hold
+					 * BTRFS_SUPER_MIRROR_MAX */
+	struct btrfsic_dev_state *dev_state;
+	u64 dev_bytenr;		/* key, physical byte num on disk */
+	u64 logical_bytenr;	/* logical byte num on disk */
+	u64 generation;
+	struct btrfs_disk_key disk_key;	/* extra info to print in case of
+					 * issues, will not always be correct */
+	struct list_head collision_resolving_node;	/* list node */
+	struct list_head all_blocks_node;	/* list node */
+
+	/* the following two lists contain block_link items */
+	struct list_head ref_to_list;	/* list */
+	struct list_head ref_from_list;	/* list */
+	struct btrfsic_block *next_in_same_bio;
+	void *orig_bio_private;
+	bio_end_io_t *orig_bio_end_io;
+	int submit_bio_bh_rw;
+	u64 flush_gen; /* only valid if !never_written */
+};
+
+/*
+ * Elements of this type are allocated dynamically and required because
+ * each block object can refer to and can be ref from multiple blocks.
+ * The key to lookup them in the hashtable is the dev_bytenr of
+ * the block ref to plus the one from the block referred from.
+ * The fact that they are searchable via a hashtable and that a
+ * ref_cnt is maintained is not required for the btrfs integrity
+ * check algorithm itself, it is only used to make the output more
+ * beautiful in case that an error is detected (an error is defined
+ * as a write operation to a block while that block is still referenced).
+ */
+struct btrfsic_block_link {
+	u32 magic_num;		/* only used for debug purposes */
+	u32 ref_cnt;
+	struct list_head node_ref_to;	/* list node */
+	struct list_head node_ref_from;	/* list node */
+	struct list_head collision_resolving_node;	/* list node */
+	struct btrfsic_block *block_ref_to;
+	struct btrfsic_block *block_ref_from;
+	u64 parent_generation;
+};
+
+struct btrfsic_dev_state {
+	u32 magic_num;		/* only used for debug purposes */
+	struct block_device *bdev;
+	struct btrfsic_state *state;
+	struct list_head collision_resolving_node;	/* list node */
+	struct btrfsic_block dummy_block_for_bio_bh_flush;
+	u64 last_flush_gen;
+	char name[BDEVNAME_SIZE];
+};
+
+struct btrfsic_block_hashtable {
+	struct list_head table[BTRFSIC_BLOCK_HASHTABLE_SIZE];
+};
+
+struct btrfsic_block_link_hashtable {
+	struct list_head table[BTRFSIC_BLOCK_LINK_HASHTABLE_SIZE];
+};
+
+struct btrfsic_dev_state_hashtable {
+	struct list_head table[BTRFSIC_DEV2STATE_HASHTABLE_SIZE];
+};
+
+struct btrfsic_block_data_ctx {
+	u64 start;		/* virtual bytenr */
+	u64 dev_bytenr;		/* physical bytenr on device */
+	u32 len;
+	struct btrfsic_dev_state *dev;
+	char **datav;
+	struct page **pagev;
+	void *mem_to_free;
+};
+
+/* This structure is used to implement recursion without occupying
+ * any stack space, refer to btrfsic_process_metablock() */
+struct btrfsic_stack_frame {
+	u32 magic;
+	u32 nr;
+	int error;
+	int i;
+	int limit_nesting;
+	int num_copies;
+	int mirror_num;
+	struct btrfsic_block *block;
+	struct btrfsic_block_data_ctx *block_ctx;
+	struct btrfsic_block *next_block;
+	struct btrfsic_block_data_ctx next_block_ctx;
+	struct btrfs_header *hdr;
+	struct btrfsic_stack_frame *prev;
+};
+
+/* Some state per mounted filesystem */
+struct btrfsic_state {
+	u32 print_mask;
+	int include_extent_data;
+	int csum_size;
+	struct list_head all_blocks_list;
+	struct btrfsic_block_hashtable block_hashtable;
+	struct btrfsic_block_link_hashtable block_link_hashtable;
+	struct btrfs_fs_info *fs_info;
+	u64 max_superblock_generation;
+	struct btrfsic_block *latest_superblock;
+	u32 metablock_size;
+	u32 datablock_size;
+};
+
+static void btrfsic_block_init(struct btrfsic_block *b);
+static struct btrfsic_block *btrfsic_block_alloc(void);
+static void btrfsic_block_free(struct btrfsic_block *b);
+static void btrfsic_block_link_init(struct btrfsic_block_link *n);
+static struct btrfsic_block_link *btrfsic_block_link_alloc(void);
+static void btrfsic_block_link_free(struct btrfsic_block_link *n);
+static void btrfsic_dev_state_init(struct btrfsic_dev_state *ds);
+static struct btrfsic_dev_state *btrfsic_dev_state_alloc(void);
+static void btrfsic_dev_state_free(struct btrfsic_dev_state *ds);
+static void btrfsic_block_hashtable_init(struct btrfsic_block_hashtable *h);
+static void btrfsic_block_hashtable_add(struct btrfsic_block *b,
+					struct btrfsic_block_hashtable *h);
+static void btrfsic_block_hashtable_remove(struct btrfsic_block *b);
+static struct btrfsic_block *btrfsic_block_hashtable_lookup(
+		struct block_device *bdev,
+		u64 dev_bytenr,
+		struct btrfsic_block_hashtable *h);
+static void btrfsic_block_link_hashtable_init(
+		struct btrfsic_block_link_hashtable *h);
+static void btrfsic_block_link_hashtable_add(
+		struct btrfsic_block_link *l,
+		struct btrfsic_block_link_hashtable *h);
+static void btrfsic_block_link_hashtable_remove(struct btrfsic_block_link *l);
+static struct btrfsic_block_link *btrfsic_block_link_hashtable_lookup(
+		struct block_device *bdev_ref_to,
+		u64 dev_bytenr_ref_to,
+		struct block_device *bdev_ref_from,
+		u64 dev_bytenr_ref_from,
+		struct btrfsic_block_link_hashtable *h);
+static void btrfsic_dev_state_hashtable_init(
+		struct btrfsic_dev_state_hashtable *h);
+static void btrfsic_dev_state_hashtable_add(
+		struct btrfsic_dev_state *ds,
+		struct btrfsic_dev_state_hashtable *h);
+static void btrfsic_dev_state_hashtable_remove(struct btrfsic_dev_state *ds);
+static struct btrfsic_dev_state *btrfsic_dev_state_hashtable_lookup(dev_t dev,
+		struct btrfsic_dev_state_hashtable *h);
+static struct btrfsic_stack_frame *btrfsic_stack_frame_alloc(void);
+static void btrfsic_stack_frame_free(struct btrfsic_stack_frame *sf);
+static int btrfsic_process_superblock(struct btrfsic_state *state,
+				      struct btrfs_fs_devices *fs_devices);
+static int btrfsic_process_metablock(struct btrfsic_state *state,
+				     struct btrfsic_block *block,
+				     struct btrfsic_block_data_ctx *block_ctx,
+				     int limit_nesting, int force_iodone_flag);
+static void btrfsic_read_from_block_data(
+	struct btrfsic_block_data_ctx *block_ctx,
+	void *dst, u32 offset, size_t len);
+static int btrfsic_create_link_to_next_block(
+		struct btrfsic_state *state,
+		struct btrfsic_block *block,
+		struct btrfsic_block_data_ctx
+		*block_ctx, u64 next_bytenr,
+		int limit_nesting,
+		struct btrfsic_block_data_ctx *next_block_ctx,
+		struct btrfsic_block **next_blockp,
+		int force_iodone_flag,
+		int *num_copiesp, int *mirror_nump,
+		struct btrfs_disk_key *disk_key,
+		u64 parent_generation);
+static int btrfsic_handle_extent_data(struct btrfsic_state *state,
+				      struct btrfsic_block *block,
+				      struct btrfsic_block_data_ctx *block_ctx,
+				      u32 item_offset, int force_iodone_flag);
+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 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);
+static void btrfsic_dump_database(struct btrfsic_state *state);
+static int btrfsic_test_for_metadata(struct btrfsic_state *state,
+				     char **datav, unsigned int num_pages);
+static void btrfsic_process_written_block(struct btrfsic_dev_state *dev_state,
+					  u64 dev_bytenr, char **mapped_datav,
+					  unsigned int num_pages,
+					  struct bio *bio, int *bio_is_patched,
+					  int submit_bio_bh_rw);
+static int btrfsic_process_written_superblock(
+		struct btrfsic_state *state,
+		struct btrfsic_block *const block,
+		struct btrfs_super_block *const super_hdr);
+static void btrfsic_bio_end_io(struct bio *bp);
+static int btrfsic_is_block_ref_by_superblock(const struct btrfsic_state *state,
+					      const struct btrfsic_block *block,
+					      int recursion_level);
+static int btrfsic_check_all_ref_blocks(struct btrfsic_state *state,
+					struct btrfsic_block *const block,
+					int recursion_level);
+static void btrfsic_print_add_link(const struct btrfsic_state *state,
+				   const struct btrfsic_block_link *l);
+static void btrfsic_print_rem_link(const struct btrfsic_state *state,
+				   const struct btrfsic_block_link *l);
+static char btrfsic_get_block_type(const struct btrfsic_state *state,
+				   const struct btrfsic_block *block);
+static void btrfsic_dump_tree(const struct btrfsic_state *state);
+static void btrfsic_dump_tree_sub(const struct btrfsic_state *state,
+				  const struct btrfsic_block *block,
+				  int indent_level);
+static struct btrfsic_block_link *btrfsic_block_link_lookup_or_add(
+		struct btrfsic_state *state,
+		struct btrfsic_block_data_ctx *next_block_ctx,
+		struct btrfsic_block *next_block,
+		struct btrfsic_block *from_block,
+		u64 parent_generation);
+static struct btrfsic_block *btrfsic_block_lookup_or_add(
+		struct btrfsic_state *state,
+		struct btrfsic_block_data_ctx *block_ctx,
+		const char *additional_string,
+		int is_metadata,
+		int is_iodone,
+		int never_written,
+		int mirror_num,
+		int *was_created);
+static int btrfsic_process_superblock_dev_mirror(
+		struct btrfsic_state *state,
+		struct btrfsic_dev_state *dev_state,
+		struct btrfs_device *device,
+		int superblock_mirror_num,
+		struct btrfsic_dev_state **selected_dev_state,
+		struct btrfs_super_block *selected_super);
+static struct btrfsic_dev_state *btrfsic_dev_state_lookup(dev_t dev);
+static void btrfsic_cmp_log_and_dev_bytenr(struct btrfsic_state *state,
+					   u64 bytenr,
+					   struct btrfsic_dev_state *dev_state,
+					   u64 dev_bytenr);
+
+static struct mutex btrfsic_mutex;
+static int btrfsic_is_initialized;
+static struct btrfsic_dev_state_hashtable btrfsic_dev_state_hashtable;
+
+
+static void btrfsic_block_init(struct btrfsic_block *b)
+{
+	b->magic_num = BTRFSIC_BLOCK_MAGIC_NUMBER;
+	b->dev_state = NULL;
+	b->dev_bytenr = 0;
+	b->logical_bytenr = 0;
+	b->generation = BTRFSIC_GENERATION_UNKNOWN;
+	b->disk_key.objectid = 0;
+	b->disk_key.type = 0;
+	b->disk_key.offset = 0;
+	b->is_metadata = 0;
+	b->is_superblock = 0;
+	b->is_iodone = 0;
+	b->iodone_w_error = 0;
+	b->never_written = 0;
+	b->mirror_num = 0;
+	b->next_in_same_bio = NULL;
+	b->orig_bio_private = NULL;
+	b->orig_bio_end_io = NULL;
+	INIT_LIST_HEAD(&b->collision_resolving_node);
+	INIT_LIST_HEAD(&b->all_blocks_node);
+	INIT_LIST_HEAD(&b->ref_to_list);
+	INIT_LIST_HEAD(&b->ref_from_list);
+	b->submit_bio_bh_rw = 0;
+	b->flush_gen = 0;
+}
+
+static struct btrfsic_block *btrfsic_block_alloc(void)
+{
+	struct btrfsic_block *b;
+
+	b = kzalloc(sizeof(*b), GFP_NOFS);
+	if (NULL != b)
+		btrfsic_block_init(b);
+
+	return b;
+}
+
+static void btrfsic_block_free(struct btrfsic_block *b)
+{
+	BUG_ON(!(NULL == b || BTRFSIC_BLOCK_MAGIC_NUMBER == b->magic_num));
+	kfree(b);
+}
+
+static void btrfsic_block_link_init(struct btrfsic_block_link *l)
+{
+	l->magic_num = BTRFSIC_BLOCK_LINK_MAGIC_NUMBER;
+	l->ref_cnt = 1;
+	INIT_LIST_HEAD(&l->node_ref_to);
+	INIT_LIST_HEAD(&l->node_ref_from);
+	INIT_LIST_HEAD(&l->collision_resolving_node);
+	l->block_ref_to = NULL;
+	l->block_ref_from = NULL;
+}
+
+static struct btrfsic_block_link *btrfsic_block_link_alloc(void)
+{
+	struct btrfsic_block_link *l;
+
+	l = kzalloc(sizeof(*l), GFP_NOFS);
+	if (NULL != l)
+		btrfsic_block_link_init(l);
+
+	return l;
+}
+
+static void btrfsic_block_link_free(struct btrfsic_block_link *l)
+{
+	BUG_ON(!(NULL == l || BTRFSIC_BLOCK_LINK_MAGIC_NUMBER == l->magic_num));
+	kfree(l);
+}
+
+static void btrfsic_dev_state_init(struct btrfsic_dev_state *ds)
+{
+	ds->magic_num = BTRFSIC_DEV2STATE_MAGIC_NUMBER;
+	ds->bdev = NULL;
+	ds->state = NULL;
+	ds->name[0] = '\0';
+	INIT_LIST_HEAD(&ds->collision_resolving_node);
+	ds->last_flush_gen = 0;
+	btrfsic_block_init(&ds->dummy_block_for_bio_bh_flush);
+	ds->dummy_block_for_bio_bh_flush.is_iodone = 1;
+	ds->dummy_block_for_bio_bh_flush.dev_state = ds;
+}
+
+static struct btrfsic_dev_state *btrfsic_dev_state_alloc(void)
+{
+	struct btrfsic_dev_state *ds;
+
+	ds = kzalloc(sizeof(*ds), GFP_NOFS);
+	if (NULL != ds)
+		btrfsic_dev_state_init(ds);
+
+	return ds;
+}
+
+static void btrfsic_dev_state_free(struct btrfsic_dev_state *ds)
+{
+	BUG_ON(!(NULL == ds ||
+		 BTRFSIC_DEV2STATE_MAGIC_NUMBER == ds->magic_num));
+	kfree(ds);
+}
+
+static void btrfsic_block_hashtable_init(struct btrfsic_block_hashtable *h)
+{
+	int i;
+
+	for (i = 0; i < BTRFSIC_BLOCK_HASHTABLE_SIZE; i++)
+		INIT_LIST_HEAD(h->table + i);
+}
+
+static void btrfsic_block_hashtable_add(struct btrfsic_block *b,
+					struct btrfsic_block_hashtable *h)
+{
+	const unsigned int hashval =
+	    (((unsigned int)(b->dev_bytenr >> 16)) ^
+	     ((unsigned int)((uintptr_t)b->dev_state->bdev))) &
+	     (BTRFSIC_BLOCK_HASHTABLE_SIZE - 1);
+
+	list_add(&b->collision_resolving_node, h->table + hashval);
+}
+
+static void btrfsic_block_hashtable_remove(struct btrfsic_block *b)
+{
+	list_del(&b->collision_resolving_node);
+}
+
+static struct btrfsic_block *btrfsic_block_hashtable_lookup(
+		struct block_device *bdev,
+		u64 dev_bytenr,
+		struct btrfsic_block_hashtable *h)
+{
+	const unsigned int hashval =
+	    (((unsigned int)(dev_bytenr >> 16)) ^
+	     ((unsigned int)((uintptr_t)bdev))) &
+	     (BTRFSIC_BLOCK_HASHTABLE_SIZE - 1);
+	struct btrfsic_block *b;
+
+	list_for_each_entry(b, h->table + hashval, collision_resolving_node) {
+		if (b->dev_state->bdev == bdev && b->dev_bytenr == dev_bytenr)
+			return b;
+	}
+
+	return NULL;
+}
+
+static void btrfsic_block_link_hashtable_init(
+		struct btrfsic_block_link_hashtable *h)
+{
+	int i;
+
+	for (i = 0; i < BTRFSIC_BLOCK_LINK_HASHTABLE_SIZE; i++)
+		INIT_LIST_HEAD(h->table + i);
+}
+
+static void btrfsic_block_link_hashtable_add(
+		struct btrfsic_block_link *l,
+		struct btrfsic_block_link_hashtable *h)
+{
+	const unsigned int hashval =
+	    (((unsigned int)(l->block_ref_to->dev_bytenr >> 16)) ^
+	     ((unsigned int)(l->block_ref_from->dev_bytenr >> 16)) ^
+	     ((unsigned int)((uintptr_t)l->block_ref_to->dev_state->bdev)) ^
+	     ((unsigned int)((uintptr_t)l->block_ref_from->dev_state->bdev)))
+	     & (BTRFSIC_BLOCK_LINK_HASHTABLE_SIZE - 1);
+
+	BUG_ON(NULL == l->block_ref_to);
+	BUG_ON(NULL == l->block_ref_from);
+	list_add(&l->collision_resolving_node, h->table + hashval);
+}
+
+static void btrfsic_block_link_hashtable_remove(struct btrfsic_block_link *l)
+{
+	list_del(&l->collision_resolving_node);
+}
+
+static struct btrfsic_block_link *btrfsic_block_link_hashtable_lookup(
+		struct block_device *bdev_ref_to,
+		u64 dev_bytenr_ref_to,
+		struct block_device *bdev_ref_from,
+		u64 dev_bytenr_ref_from,
+		struct btrfsic_block_link_hashtable *h)
+{
+	const unsigned int hashval =
+	    (((unsigned int)(dev_bytenr_ref_to >> 16)) ^
+	     ((unsigned int)(dev_bytenr_ref_from >> 16)) ^
+	     ((unsigned int)((uintptr_t)bdev_ref_to)) ^
+	     ((unsigned int)((uintptr_t)bdev_ref_from))) &
+	     (BTRFSIC_BLOCK_LINK_HASHTABLE_SIZE - 1);
+	struct btrfsic_block_link *l;
+
+	list_for_each_entry(l, h->table + hashval, collision_resolving_node) {
+		BUG_ON(NULL == l->block_ref_to);
+		BUG_ON(NULL == l->block_ref_from);
+		if (l->block_ref_to->dev_state->bdev == bdev_ref_to &&
+		    l->block_ref_to->dev_bytenr == dev_bytenr_ref_to &&
+		    l->block_ref_from->dev_state->bdev == bdev_ref_from &&
+		    l->block_ref_from->dev_bytenr == dev_bytenr_ref_from)
+			return l;
+	}
+
+	return NULL;
+}
+
+static void btrfsic_dev_state_hashtable_init(
+		struct btrfsic_dev_state_hashtable *h)
+{
+	int i;
+
+	for (i = 0; i < BTRFSIC_DEV2STATE_HASHTABLE_SIZE; i++)
+		INIT_LIST_HEAD(h->table + i);
+}
+
+static void btrfsic_dev_state_hashtable_add(
+		struct btrfsic_dev_state *ds,
+		struct btrfsic_dev_state_hashtable *h)
+{
+	const unsigned int hashval =
+	    (((unsigned int)((uintptr_t)ds->bdev->bd_dev)) &
+	     (BTRFSIC_DEV2STATE_HASHTABLE_SIZE - 1));
+
+	list_add(&ds->collision_resolving_node, h->table + hashval);
+}
+
+static void btrfsic_dev_state_hashtable_remove(struct btrfsic_dev_state *ds)
+{
+	list_del(&ds->collision_resolving_node);
+}
+
+static struct btrfsic_dev_state *btrfsic_dev_state_hashtable_lookup(dev_t dev,
+		struct btrfsic_dev_state_hashtable *h)
+{
+	const unsigned int hashval =
+		dev & (BTRFSIC_DEV2STATE_HASHTABLE_SIZE - 1);
+	struct btrfsic_dev_state *ds;
+
+	list_for_each_entry(ds, h->table + hashval, collision_resolving_node) {
+		if (ds->bdev->bd_dev == dev)
+			return ds;
+	}
+
+	return NULL;
+}
+
+static int btrfsic_process_superblock(struct btrfsic_state *state,
+				      struct btrfs_fs_devices *fs_devices)
+{
+	struct btrfs_super_block *selected_super;
+	struct list_head *dev_head = &fs_devices->devices;
+	struct btrfs_device *device;
+	struct btrfsic_dev_state *selected_dev_state = NULL;
+	int ret = 0;
+	int pass;
+
+	selected_super = kzalloc(sizeof(*selected_super), GFP_NOFS);
+	if (!selected_super)
+		return -ENOMEM;
+
+	list_for_each_entry(device, dev_head, dev_list) {
+		int i;
+		struct btrfsic_dev_state *dev_state;
+
+		if (!device->bdev || !device->name)
+			continue;
+
+		dev_state = btrfsic_dev_state_lookup(device->bdev->bd_dev);
+		BUG_ON(NULL == dev_state);
+		for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
+			ret = btrfsic_process_superblock_dev_mirror(
+					state, dev_state, device, i,
+					&selected_dev_state, selected_super);
+			if (0 != ret && 0 == i) {
+				kfree(selected_super);
+				return ret;
+			}
+		}
+	}
+
+	if (NULL == state->latest_superblock) {
+		pr_info("btrfsic: no superblock found!\n");
+		kfree(selected_super);
+		return -1;
+	}
+
+	state->csum_size = btrfs_super_csum_size(selected_super);
+
+	for (pass = 0; pass < 3; pass++) {
+		int num_copies;
+		int mirror_num;
+		u64 next_bytenr;
+
+		switch (pass) {
+		case 0:
+			next_bytenr = btrfs_super_root(selected_super);
+			if (state->print_mask &
+			    BTRFSIC_PRINT_MASK_ROOT_CHUNK_LOG_TREE_LOCATION)
+				pr_info("root@%llu\n", next_bytenr);
+			break;
+		case 1:
+			next_bytenr = btrfs_super_chunk_root(selected_super);
+			if (state->print_mask &
+			    BTRFSIC_PRINT_MASK_ROOT_CHUNK_LOG_TREE_LOCATION)
+				pr_info("chunk@%llu\n", next_bytenr);
+			break;
+		case 2:
+			next_bytenr = btrfs_super_log_root(selected_super);
+			if (0 == next_bytenr)
+				continue;
+			if (state->print_mask &
+			    BTRFSIC_PRINT_MASK_ROOT_CHUNK_LOG_TREE_LOCATION)
+				pr_info("log@%llu\n", next_bytenr);
+			break;
+		}
+
+		num_copies = btrfs_num_copies(state->fs_info, next_bytenr,
+					      state->metablock_size);
+		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
+			pr_info("num_copies(log_bytenr=%llu) = %d\n",
+			       next_bytenr, num_copies);
+
+		for (mirror_num = 1; mirror_num <= num_copies; mirror_num++) {
+			struct btrfsic_block *next_block;
+			struct btrfsic_block_data_ctx tmp_next_block_ctx;
+			struct btrfsic_block_link *l;
+
+			ret = btrfsic_map_block(state, next_bytenr,
+						state->metablock_size,
+						&tmp_next_block_ctx,
+						mirror_num);
+			if (ret) {
+				pr_info("btrfsic: btrfsic_map_block(root @%llu, mirror %d) failed!\n",
+				       next_bytenr, mirror_num);
+				kfree(selected_super);
+				return -1;
+			}
+
+			next_block = btrfsic_block_hashtable_lookup(
+					tmp_next_block_ctx.dev->bdev,
+					tmp_next_block_ctx.dev_bytenr,
+					&state->block_hashtable);
+			BUG_ON(NULL == next_block);
+
+			l = btrfsic_block_link_hashtable_lookup(
+					tmp_next_block_ctx.dev->bdev,
+					tmp_next_block_ctx.dev_bytenr,
+					state->latest_superblock->dev_state->
+					bdev,
+					state->latest_superblock->dev_bytenr,
+					&state->block_link_hashtable);
+			BUG_ON(NULL == l);
+
+			ret = btrfsic_read_block(state, &tmp_next_block_ctx);
+			if (ret < (int)PAGE_SIZE) {
+				pr_info("btrfsic: read @logical %llu failed!\n",
+				       tmp_next_block_ctx.start);
+				btrfsic_release_block_ctx(&tmp_next_block_ctx);
+				kfree(selected_super);
+				return -1;
+			}
+
+			ret = btrfsic_process_metablock(state,
+							next_block,
+							&tmp_next_block_ctx,
+							BTRFS_MAX_LEVEL + 3, 1);
+			btrfsic_release_block_ctx(&tmp_next_block_ctx);
+		}
+	}
+
+	kfree(selected_super);
+	return ret;
+}
+
+static int btrfsic_process_superblock_dev_mirror(
+		struct btrfsic_state *state,
+		struct btrfsic_dev_state *dev_state,
+		struct btrfs_device *device,
+		int superblock_mirror_num,
+		struct btrfsic_dev_state **selected_dev_state,
+		struct btrfs_super_block *selected_super)
+{
+	struct btrfs_fs_info *fs_info = state->fs_info;
+	struct btrfs_super_block *super_tmp;
+	u64 dev_bytenr;
+	struct btrfsic_block *superblock_tmp;
+	int pass;
+	struct block_device *const superblock_bdev = device->bdev;
+	struct page *page;
+	struct address_space *mapping = superblock_bdev->bd_inode->i_mapping;
+	int ret = 0;
+
+	/* super block bytenr is always the unmapped device bytenr */
+	dev_bytenr = btrfs_sb_offset(superblock_mirror_num);
+	if (dev_bytenr + BTRFS_SUPER_INFO_SIZE > device->commit_total_bytes)
+		return -1;
+
+	page = read_cache_page_gfp(mapping, dev_bytenr >> PAGE_SHIFT, GFP_NOFS);
+	if (IS_ERR(page))
+		return -1;
+
+	super_tmp = page_address(page);
+
+	if (btrfs_super_bytenr(super_tmp) != dev_bytenr ||
+	    btrfs_super_magic(super_tmp) != BTRFS_MAGIC ||
+	    memcmp(device->uuid, super_tmp->dev_item.uuid, BTRFS_UUID_SIZE) ||
+	    btrfs_super_nodesize(super_tmp) != state->metablock_size ||
+	    btrfs_super_sectorsize(super_tmp) != state->datablock_size) {
+		ret = 0;
+		goto out;
+	}
+
+	superblock_tmp =
+	    btrfsic_block_hashtable_lookup(superblock_bdev,
+					   dev_bytenr,
+					   &state->block_hashtable);
+	if (NULL == superblock_tmp) {
+		superblock_tmp = btrfsic_block_alloc();
+		if (NULL == superblock_tmp) {
+			ret = -1;
+			goto out;
+		}
+		/* for superblock, only the dev_bytenr makes sense */
+		superblock_tmp->dev_bytenr = dev_bytenr;
+		superblock_tmp->dev_state = dev_state;
+		superblock_tmp->logical_bytenr = dev_bytenr;
+		superblock_tmp->generation = btrfs_super_generation(super_tmp);
+		superblock_tmp->is_metadata = 1;
+		superblock_tmp->is_superblock = 1;
+		superblock_tmp->is_iodone = 1;
+		superblock_tmp->never_written = 0;
+		superblock_tmp->mirror_num = 1 + superblock_mirror_num;
+		if (state->print_mask & BTRFSIC_PRINT_MASK_SUPERBLOCK_WRITE)
+			btrfs_info_in_rcu(fs_info,
+				"new initial S-block (bdev %p, %s) @%llu (%s/%llu/%d)",
+				     superblock_bdev,
+				     rcu_str_deref(device->name), dev_bytenr,
+				     dev_state->name, dev_bytenr,
+				     superblock_mirror_num);
+		list_add(&superblock_tmp->all_blocks_node,
+			 &state->all_blocks_list);
+		btrfsic_block_hashtable_add(superblock_tmp,
+					    &state->block_hashtable);
+	}
+
+	/* select the one with the highest generation field */
+	if (btrfs_super_generation(super_tmp) >
+	    state->max_superblock_generation ||
+	    0 == state->max_superblock_generation) {
+		memcpy(selected_super, super_tmp, sizeof(*selected_super));
+		*selected_dev_state = dev_state;
+		state->max_superblock_generation =
+		    btrfs_super_generation(super_tmp);
+		state->latest_superblock = superblock_tmp;
+	}
+
+	for (pass = 0; pass < 3; pass++) {
+		u64 next_bytenr;
+		int num_copies;
+		int mirror_num;
+		const char *additional_string = NULL;
+		struct btrfs_disk_key tmp_disk_key;
+
+		tmp_disk_key.type = BTRFS_ROOT_ITEM_KEY;
+		tmp_disk_key.offset = 0;
+		switch (pass) {
+		case 0:
+			btrfs_set_disk_key_objectid(&tmp_disk_key,
+						    BTRFS_ROOT_TREE_OBJECTID);
+			additional_string = "initial root ";
+			next_bytenr = btrfs_super_root(super_tmp);
+			break;
+		case 1:
+			btrfs_set_disk_key_objectid(&tmp_disk_key,
+						    BTRFS_CHUNK_TREE_OBJECTID);
+			additional_string = "initial chunk ";
+			next_bytenr = btrfs_super_chunk_root(super_tmp);
+			break;
+		case 2:
+			btrfs_set_disk_key_objectid(&tmp_disk_key,
+						    BTRFS_TREE_LOG_OBJECTID);
+			additional_string = "initial log ";
+			next_bytenr = btrfs_super_log_root(super_tmp);
+			if (0 == next_bytenr)
+				continue;
+			break;
+		}
+
+		num_copies = btrfs_num_copies(fs_info, next_bytenr,
+					      state->metablock_size);
+		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
+			pr_info("num_copies(log_bytenr=%llu) = %d\n",
+			       next_bytenr, num_copies);
+		for (mirror_num = 1; mirror_num <= num_copies; mirror_num++) {
+			struct btrfsic_block *next_block;
+			struct btrfsic_block_data_ctx tmp_next_block_ctx;
+			struct btrfsic_block_link *l;
+
+			if (btrfsic_map_block(state, next_bytenr,
+					      state->metablock_size,
+					      &tmp_next_block_ctx,
+					      mirror_num)) {
+				pr_info("btrfsic: btrfsic_map_block(bytenr @%llu, mirror %d) failed!\n",
+				       next_bytenr, mirror_num);
+				ret = -1;
+				goto out;
+			}
+
+			next_block = btrfsic_block_lookup_or_add(
+					state, &tmp_next_block_ctx,
+					additional_string, 1, 1, 0,
+					mirror_num, NULL);
+			if (NULL == next_block) {
+				btrfsic_release_block_ctx(&tmp_next_block_ctx);
+				ret = -1;
+				goto out;
+			}
+
+			next_block->disk_key = tmp_disk_key;
+			next_block->generation = BTRFSIC_GENERATION_UNKNOWN;
+			l = btrfsic_block_link_lookup_or_add(
+					state, &tmp_next_block_ctx,
+					next_block, superblock_tmp,
+					BTRFSIC_GENERATION_UNKNOWN);
+			btrfsic_release_block_ctx(&tmp_next_block_ctx);
+			if (NULL == l) {
+				ret = -1;
+				goto out;
+			}
+		}
+	}
+	if (state->print_mask & BTRFSIC_PRINT_MASK_INITIAL_ALL_TREES)
+		btrfsic_dump_tree_sub(state, superblock_tmp, 0);
+
+out:
+	put_page(page);
+	return ret;
+}
+
+static struct btrfsic_stack_frame *btrfsic_stack_frame_alloc(void)
+{
+	struct btrfsic_stack_frame *sf;
+
+	sf = kzalloc(sizeof(*sf), GFP_NOFS);
+	if (sf)
+		sf->magic = BTRFSIC_BLOCK_STACK_FRAME_MAGIC_NUMBER;
+	return sf;
+}
+
+static void btrfsic_stack_frame_free(struct btrfsic_stack_frame *sf)
+{
+	BUG_ON(!(NULL == sf ||
+		 BTRFSIC_BLOCK_STACK_FRAME_MAGIC_NUMBER == sf->magic));
+	kfree(sf);
+}
+
+static noinline_for_stack int btrfsic_process_metablock(
+		struct btrfsic_state *state,
+		struct btrfsic_block *const first_block,
+		struct btrfsic_block_data_ctx *const first_block_ctx,
+		int first_limit_nesting, int force_iodone_flag)
+{
+	struct btrfsic_stack_frame initial_stack_frame = { 0 };
+	struct btrfsic_stack_frame *sf;
+	struct btrfsic_stack_frame *next_stack;
+	struct btrfs_header *const first_hdr =
+		(struct btrfs_header *)first_block_ctx->datav[0];
+
+	BUG_ON(!first_hdr);
+	sf = &initial_stack_frame;
+	sf->error = 0;
+	sf->i = -1;
+	sf->limit_nesting = first_limit_nesting;
+	sf->block = first_block;
+	sf->block_ctx = first_block_ctx;
+	sf->next_block = NULL;
+	sf->hdr = first_hdr;
+	sf->prev = NULL;
+
+continue_with_new_stack_frame:
+	sf->block->generation = le64_to_cpu(sf->hdr->generation);
+	if (0 == sf->hdr->level) {
+		struct btrfs_leaf *const leafhdr =
+		    (struct btrfs_leaf *)sf->hdr;
+
+		if (-1 == sf->i) {
+			sf->nr = btrfs_stack_header_nritems(&leafhdr->header);
+
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+				pr_info("leaf %llu items %d generation %llu owner %llu\n",
+				       sf->block_ctx->start, sf->nr,
+				       btrfs_stack_header_generation(
+					       &leafhdr->header),
+				       btrfs_stack_header_owner(
+					       &leafhdr->header));
+		}
+
+continue_with_current_leaf_stack_frame:
+		if (0 == sf->num_copies || sf->mirror_num > sf->num_copies) {
+			sf->i++;
+			sf->num_copies = 0;
+		}
+
+		if (sf->i < sf->nr) {
+			struct btrfs_item disk_item;
+			u32 disk_item_offset =
+				(uintptr_t)(leafhdr->items + sf->i) -
+				(uintptr_t)leafhdr;
+			struct btrfs_disk_key *disk_key;
+			u8 type;
+			u32 item_offset;
+			u32 item_size;
+
+			if (disk_item_offset + sizeof(struct btrfs_item) >
+			    sf->block_ctx->len) {
+leaf_item_out_of_bounce_error:
+				pr_info("btrfsic: leaf item out of bounce at logical %llu, dev %s\n",
+				       sf->block_ctx->start,
+				       sf->block_ctx->dev->name);
+				goto one_stack_frame_backwards;
+			}
+			btrfsic_read_from_block_data(sf->block_ctx,
+						     &disk_item,
+						     disk_item_offset,
+						     sizeof(struct btrfs_item));
+			item_offset = btrfs_stack_item_offset(&disk_item);
+			item_size = btrfs_stack_item_size(&disk_item);
+			disk_key = &disk_item.key;
+			type = btrfs_disk_key_type(disk_key);
+
+			if (BTRFS_ROOT_ITEM_KEY == type) {
+				struct btrfs_root_item root_item;
+				u32 root_item_offset;
+				u64 next_bytenr;
+
+				root_item_offset = item_offset +
+					offsetof(struct btrfs_leaf, items);
+				if (root_item_offset + item_size >
+				    sf->block_ctx->len)
+					goto leaf_item_out_of_bounce_error;
+				btrfsic_read_from_block_data(
+					sf->block_ctx, &root_item,
+					root_item_offset,
+					item_size);
+				next_bytenr = btrfs_root_bytenr(&root_item);
+
+				sf->error =
+				    btrfsic_create_link_to_next_block(
+						state,
+						sf->block,
+						sf->block_ctx,
+						next_bytenr,
+						sf->limit_nesting,
+						&sf->next_block_ctx,
+						&sf->next_block,
+						force_iodone_flag,
+						&sf->num_copies,
+						&sf->mirror_num,
+						disk_key,
+						btrfs_root_generation(
+						&root_item));
+				if (sf->error)
+					goto one_stack_frame_backwards;
+
+				if (NULL != sf->next_block) {
+					struct btrfs_header *const next_hdr =
+					    (struct btrfs_header *)
+					    sf->next_block_ctx.datav[0];
+
+					next_stack =
+					    btrfsic_stack_frame_alloc();
+					if (NULL == next_stack) {
+						sf->error = -1;
+						btrfsic_release_block_ctx(
+								&sf->
+								next_block_ctx);
+						goto one_stack_frame_backwards;
+					}
+
+					next_stack->i = -1;
+					next_stack->block = sf->next_block;
+					next_stack->block_ctx =
+					    &sf->next_block_ctx;
+					next_stack->next_block = NULL;
+					next_stack->hdr = next_hdr;
+					next_stack->limit_nesting =
+					    sf->limit_nesting - 1;
+					next_stack->prev = sf;
+					sf = next_stack;
+					goto continue_with_new_stack_frame;
+				}
+			} else if (BTRFS_EXTENT_DATA_KEY == type &&
+				   state->include_extent_data) {
+				sf->error = btrfsic_handle_extent_data(
+						state,
+						sf->block,
+						sf->block_ctx,
+						item_offset,
+						force_iodone_flag);
+				if (sf->error)
+					goto one_stack_frame_backwards;
+			}
+
+			goto continue_with_current_leaf_stack_frame;
+		}
+	} else {
+		struct btrfs_node *const nodehdr = (struct btrfs_node *)sf->hdr;
+
+		if (-1 == sf->i) {
+			sf->nr = btrfs_stack_header_nritems(&nodehdr->header);
+
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+				pr_info("node %llu level %d items %d generation %llu owner %llu\n",
+				       sf->block_ctx->start,
+				       nodehdr->header.level, sf->nr,
+				       btrfs_stack_header_generation(
+				       &nodehdr->header),
+				       btrfs_stack_header_owner(
+				       &nodehdr->header));
+		}
+
+continue_with_current_node_stack_frame:
+		if (0 == sf->num_copies || sf->mirror_num > sf->num_copies) {
+			sf->i++;
+			sf->num_copies = 0;
+		}
+
+		if (sf->i < sf->nr) {
+			struct btrfs_key_ptr key_ptr;
+			u32 key_ptr_offset;
+			u64 next_bytenr;
+
+			key_ptr_offset = (uintptr_t)(nodehdr->ptrs + sf->i) -
+					  (uintptr_t)nodehdr;
+			if (key_ptr_offset + sizeof(struct btrfs_key_ptr) >
+			    sf->block_ctx->len) {
+				pr_info("btrfsic: node item out of bounce at logical %llu, dev %s\n",
+				       sf->block_ctx->start,
+				       sf->block_ctx->dev->name);
+				goto one_stack_frame_backwards;
+			}
+			btrfsic_read_from_block_data(
+				sf->block_ctx, &key_ptr, key_ptr_offset,
+				sizeof(struct btrfs_key_ptr));
+			next_bytenr = btrfs_stack_key_blockptr(&key_ptr);
+
+			sf->error = btrfsic_create_link_to_next_block(
+					state,
+					sf->block,
+					sf->block_ctx,
+					next_bytenr,
+					sf->limit_nesting,
+					&sf->next_block_ctx,
+					&sf->next_block,
+					force_iodone_flag,
+					&sf->num_copies,
+					&sf->mirror_num,
+					&key_ptr.key,
+					btrfs_stack_key_generation(&key_ptr));
+			if (sf->error)
+				goto one_stack_frame_backwards;
+
+			if (NULL != sf->next_block) {
+				struct btrfs_header *const next_hdr =
+				    (struct btrfs_header *)
+				    sf->next_block_ctx.datav[0];
+
+				next_stack = btrfsic_stack_frame_alloc();
+				if (NULL == next_stack) {
+					sf->error = -1;
+					goto one_stack_frame_backwards;
+				}
+
+				next_stack->i = -1;
+				next_stack->block = sf->next_block;
+				next_stack->block_ctx = &sf->next_block_ctx;
+				next_stack->next_block = NULL;
+				next_stack->hdr = next_hdr;
+				next_stack->limit_nesting =
+				    sf->limit_nesting - 1;
+				next_stack->prev = sf;
+				sf = next_stack;
+				goto continue_with_new_stack_frame;
+			}
+
+			goto continue_with_current_node_stack_frame;
+		}
+	}
+
+one_stack_frame_backwards:
+	if (NULL != sf->prev) {
+		struct btrfsic_stack_frame *const prev = sf->prev;
+
+		/* the one for the initial block is freed in the caller */
+		btrfsic_release_block_ctx(sf->block_ctx);
+
+		if (sf->error) {
+			prev->error = sf->error;
+			btrfsic_stack_frame_free(sf);
+			sf = prev;
+			goto one_stack_frame_backwards;
+		}
+
+		btrfsic_stack_frame_free(sf);
+		sf = prev;
+		goto continue_with_new_stack_frame;
+	} else {
+		BUG_ON(&initial_stack_frame != sf);
+	}
+
+	return sf->error;
+}
+
+static void btrfsic_read_from_block_data(
+	struct btrfsic_block_data_ctx *block_ctx,
+	void *dstv, u32 offset, size_t len)
+{
+	size_t cur;
+	size_t pgoff;
+	char *kaddr;
+	char *dst = (char *)dstv;
+	size_t start_offset = offset_in_page(block_ctx->start);
+	unsigned long i = (start_offset + offset) >> PAGE_SHIFT;
+
+	WARN_ON(offset + len > block_ctx->len);
+	pgoff = offset_in_page(start_offset + offset);
+
+	while (len > 0) {
+		cur = min(len, ((size_t)PAGE_SIZE - pgoff));
+		BUG_ON(i >= DIV_ROUND_UP(block_ctx->len, PAGE_SIZE));
+		kaddr = block_ctx->datav[i];
+		memcpy(dst, kaddr + pgoff, cur);
+
+		dst += cur;
+		len -= cur;
+		pgoff = 0;
+		i++;
+	}
+}
+
+static int btrfsic_create_link_to_next_block(
+		struct btrfsic_state *state,
+		struct btrfsic_block *block,
+		struct btrfsic_block_data_ctx *block_ctx,
+		u64 next_bytenr,
+		int limit_nesting,
+		struct btrfsic_block_data_ctx *next_block_ctx,
+		struct btrfsic_block **next_blockp,
+		int force_iodone_flag,
+		int *num_copiesp, int *mirror_nump,
+		struct btrfs_disk_key *disk_key,
+		u64 parent_generation)
+{
+	struct btrfs_fs_info *fs_info = state->fs_info;
+	struct btrfsic_block *next_block = NULL;
+	int ret;
+	struct btrfsic_block_link *l;
+	int did_alloc_block_link;
+	int block_was_created;
+
+	*next_blockp = NULL;
+	if (0 == *num_copiesp) {
+		*num_copiesp = btrfs_num_copies(fs_info, next_bytenr,
+						state->metablock_size);
+		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
+			pr_info("num_copies(log_bytenr=%llu) = %d\n",
+			       next_bytenr, *num_copiesp);
+		*mirror_nump = 1;
+	}
+
+	if (*mirror_nump > *num_copiesp)
+		return 0;
+
+	if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+		pr_info("btrfsic_create_link_to_next_block(mirror_num=%d)\n",
+		       *mirror_nump);
+	ret = btrfsic_map_block(state, next_bytenr,
+				state->metablock_size,
+				next_block_ctx, *mirror_nump);
+	if (ret) {
+		pr_info("btrfsic: btrfsic_map_block(@%llu, mirror=%d) failed!\n",
+		       next_bytenr, *mirror_nump);
+		btrfsic_release_block_ctx(next_block_ctx);
+		*next_blockp = NULL;
+		return -1;
+	}
+
+	next_block = btrfsic_block_lookup_or_add(state,
+						 next_block_ctx, "referenced ",
+						 1, force_iodone_flag,
+						 !force_iodone_flag,
+						 *mirror_nump,
+						 &block_was_created);
+	if (NULL == next_block) {
+		btrfsic_release_block_ctx(next_block_ctx);
+		*next_blockp = NULL;
+		return -1;
+	}
+	if (block_was_created) {
+		l = NULL;
+		next_block->generation = BTRFSIC_GENERATION_UNKNOWN;
+	} else {
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE) {
+			if (next_block->logical_bytenr != next_bytenr &&
+			    !(!next_block->is_metadata &&
+			      0 == next_block->logical_bytenr))
+				pr_info("Referenced block @%llu (%s/%llu/%d) found in hash table, %c, bytenr mismatch (!= stored %llu).\n",
+				       next_bytenr, next_block_ctx->dev->name,
+				       next_block_ctx->dev_bytenr, *mirror_nump,
+				       btrfsic_get_block_type(state,
+							      next_block),
+				       next_block->logical_bytenr);
+			else
+				pr_info("Referenced block @%llu (%s/%llu/%d) found in hash table, %c.\n",
+				       next_bytenr, next_block_ctx->dev->name,
+				       next_block_ctx->dev_bytenr, *mirror_nump,
+				       btrfsic_get_block_type(state,
+							      next_block));
+		}
+		next_block->logical_bytenr = next_bytenr;
+
+		next_block->mirror_num = *mirror_nump;
+		l = btrfsic_block_link_hashtable_lookup(
+				next_block_ctx->dev->bdev,
+				next_block_ctx->dev_bytenr,
+				block_ctx->dev->bdev,
+				block_ctx->dev_bytenr,
+				&state->block_link_hashtable);
+	}
+
+	next_block->disk_key = *disk_key;
+	if (NULL == l) {
+		l = btrfsic_block_link_alloc();
+		if (NULL == l) {
+			btrfsic_release_block_ctx(next_block_ctx);
+			*next_blockp = NULL;
+			return -1;
+		}
+
+		did_alloc_block_link = 1;
+		l->block_ref_to = next_block;
+		l->block_ref_from = block;
+		l->ref_cnt = 1;
+		l->parent_generation = parent_generation;
+
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+			btrfsic_print_add_link(state, l);
+
+		list_add(&l->node_ref_to, &block->ref_to_list);
+		list_add(&l->node_ref_from, &next_block->ref_from_list);
+
+		btrfsic_block_link_hashtable_add(l,
+						 &state->block_link_hashtable);
+	} else {
+		did_alloc_block_link = 0;
+		if (0 == limit_nesting) {
+			l->ref_cnt++;
+			l->parent_generation = parent_generation;
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+				btrfsic_print_add_link(state, l);
+		}
+	}
+
+	if (limit_nesting > 0 && did_alloc_block_link) {
+		ret = btrfsic_read_block(state, next_block_ctx);
+		if (ret < (int)next_block_ctx->len) {
+			pr_info("btrfsic: read block @logical %llu failed!\n",
+			       next_bytenr);
+			btrfsic_release_block_ctx(next_block_ctx);
+			*next_blockp = NULL;
+			return -1;
+		}
+
+		*next_blockp = next_block;
+	} else {
+		*next_blockp = NULL;
+	}
+	(*mirror_nump)++;
+
+	return 0;
+}
+
+static int btrfsic_handle_extent_data(
+		struct btrfsic_state *state,
+		struct btrfsic_block *block,
+		struct btrfsic_block_data_ctx *block_ctx,
+		u32 item_offset, int force_iodone_flag)
+{
+	struct btrfs_fs_info *fs_info = state->fs_info;
+	struct btrfs_file_extent_item file_extent_item;
+	u64 file_extent_item_offset;
+	u64 next_bytenr;
+	u64 num_bytes;
+	u64 generation;
+	struct btrfsic_block_link *l;
+	int ret;
+
+	file_extent_item_offset = offsetof(struct btrfs_leaf, items) +
+				  item_offset;
+	if (file_extent_item_offset +
+	    offsetof(struct btrfs_file_extent_item, disk_num_bytes) >
+	    block_ctx->len) {
+		pr_info("btrfsic: file item out of bounce at logical %llu, dev %s\n",
+		       block_ctx->start, block_ctx->dev->name);
+		return -1;
+	}
+
+	btrfsic_read_from_block_data(block_ctx, &file_extent_item,
+		file_extent_item_offset,
+		offsetof(struct btrfs_file_extent_item, disk_num_bytes));
+	if (BTRFS_FILE_EXTENT_REG != file_extent_item.type ||
+	    btrfs_stack_file_extent_disk_bytenr(&file_extent_item) == 0) {
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERY_VERBOSE)
+			pr_info("extent_data: type %u, disk_bytenr = %llu\n",
+			       file_extent_item.type,
+			       btrfs_stack_file_extent_disk_bytenr(
+			       &file_extent_item));
+		return 0;
+	}
+
+	if (file_extent_item_offset + sizeof(struct btrfs_file_extent_item) >
+	    block_ctx->len) {
+		pr_info("btrfsic: file item out of bounce at logical %llu, dev %s\n",
+		       block_ctx->start, block_ctx->dev->name);
+		return -1;
+	}
+	btrfsic_read_from_block_data(block_ctx, &file_extent_item,
+				     file_extent_item_offset,
+				     sizeof(struct btrfs_file_extent_item));
+	next_bytenr = btrfs_stack_file_extent_disk_bytenr(&file_extent_item);
+	if (btrfs_stack_file_extent_compression(&file_extent_item) ==
+	    BTRFS_COMPRESS_NONE) {
+		next_bytenr += btrfs_stack_file_extent_offset(&file_extent_item);
+		num_bytes = btrfs_stack_file_extent_num_bytes(&file_extent_item);
+	} else {
+		num_bytes = btrfs_stack_file_extent_disk_num_bytes(&file_extent_item);
+	}
+	generation = btrfs_stack_file_extent_generation(&file_extent_item);
+
+	if (state->print_mask & BTRFSIC_PRINT_MASK_VERY_VERBOSE)
+		pr_info("extent_data: type %u, disk_bytenr = %llu, offset = %llu, num_bytes = %llu\n",
+		       file_extent_item.type,
+		       btrfs_stack_file_extent_disk_bytenr(&file_extent_item),
+		       btrfs_stack_file_extent_offset(&file_extent_item),
+		       num_bytes);
+	while (num_bytes > 0) {
+		u32 chunk_len;
+		int num_copies;
+		int mirror_num;
+
+		if (num_bytes > state->datablock_size)
+			chunk_len = state->datablock_size;
+		else
+			chunk_len = num_bytes;
+
+		num_copies = btrfs_num_copies(fs_info, next_bytenr,
+					      state->datablock_size);
+		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
+			pr_info("num_copies(log_bytenr=%llu) = %d\n",
+			       next_bytenr, num_copies);
+		for (mirror_num = 1; mirror_num <= num_copies; mirror_num++) {
+			struct btrfsic_block_data_ctx next_block_ctx;
+			struct btrfsic_block *next_block;
+			int block_was_created;
+
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+				pr_info("btrfsic_handle_extent_data(mirror_num=%d)\n",
+					mirror_num);
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERY_VERBOSE)
+				pr_info("\tdisk_bytenr = %llu, num_bytes %u\n",
+				       next_bytenr, chunk_len);
+			ret = btrfsic_map_block(state, next_bytenr,
+						chunk_len, &next_block_ctx,
+						mirror_num);
+			if (ret) {
+				pr_info("btrfsic: btrfsic_map_block(@%llu, mirror=%d) failed!\n",
+				       next_bytenr, mirror_num);
+				return -1;
+			}
+
+			next_block = btrfsic_block_lookup_or_add(
+					state,
+					&next_block_ctx,
+					"referenced ",
+					0,
+					force_iodone_flag,
+					!force_iodone_flag,
+					mirror_num,
+					&block_was_created);
+			if (NULL == next_block) {
+				btrfsic_release_block_ctx(&next_block_ctx);
+				return -1;
+			}
+			if (!block_was_created) {
+				if ((state->print_mask &
+				     BTRFSIC_PRINT_MASK_VERBOSE) &&
+				    next_block->logical_bytenr != next_bytenr &&
+				    !(!next_block->is_metadata &&
+				      0 == next_block->logical_bytenr)) {
+					pr_info("Referenced block @%llu (%s/%llu/%d) found in hash table, D, bytenr mismatch (!= stored %llu).\n",
+					       next_bytenr,
+					       next_block_ctx.dev->name,
+					       next_block_ctx.dev_bytenr,
+					       mirror_num,
+					       next_block->logical_bytenr);
+				}
+				next_block->logical_bytenr = next_bytenr;
+				next_block->mirror_num = mirror_num;
+			}
+
+			l = btrfsic_block_link_lookup_or_add(state,
+							     &next_block_ctx,
+							     next_block, block,
+							     generation);
+			btrfsic_release_block_ctx(&next_block_ctx);
+			if (NULL == l)
+				return -1;
+		}
+
+		next_bytenr += chunk_len;
+		num_bytes -= chunk_len;
+	}
+
+	return 0;
+}
+
+static int btrfsic_map_block(struct btrfsic_state *state, u64 bytenr, u32 len,
+			     struct btrfsic_block_data_ctx *block_ctx_out,
+			     int mirror_num)
+{
+	struct btrfs_fs_info *fs_info = state->fs_info;
+	int ret;
+	u64 length;
+	struct btrfs_bio *multi = NULL;
+	struct btrfs_device *device;
+
+	length = len;
+	ret = btrfs_map_block(fs_info, BTRFS_MAP_READ,
+			      bytenr, &length, &multi, mirror_num);
+
+	if (ret) {
+		block_ctx_out->start = 0;
+		block_ctx_out->dev_bytenr = 0;
+		block_ctx_out->len = 0;
+		block_ctx_out->dev = NULL;
+		block_ctx_out->datav = NULL;
+		block_ctx_out->pagev = NULL;
+		block_ctx_out->mem_to_free = NULL;
+
+		return ret;
+	}
+
+	device = multi->stripes[0].dev;
+	if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state) ||
+	    !device->bdev || !device->name)
+		block_ctx_out->dev = NULL;
+	else
+		block_ctx_out->dev = btrfsic_dev_state_lookup(
+							device->bdev->bd_dev);
+	block_ctx_out->dev_bytenr = multi->stripes[0].physical;
+	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;
+
+	kfree(multi);
+	if (NULL == block_ctx_out->dev) {
+		ret = -ENXIO;
+		pr_info("btrfsic: error, cannot lookup dev (#1)!\n");
+	}
+
+	return ret;
+}
+
+static void btrfsic_release_block_ctx(struct btrfsic_block_data_ctx *block_ctx)
+{
+	if (block_ctx->mem_to_free) {
+		unsigned int num_pages;
+
+		BUG_ON(!block_ctx->datav);
+		BUG_ON(!block_ctx->pagev);
+		num_pages = (block_ctx->len + (u64)PAGE_SIZE - 1) >>
+			    PAGE_SHIFT;
+		while (num_pages > 0) {
+			num_pages--;
+			if (block_ctx->datav[num_pages]) {
+				kunmap(block_ctx->pagev[num_pages]);
+				block_ctx->datav[num_pages] = NULL;
+			}
+			if (block_ctx->pagev[num_pages]) {
+				__free_page(block_ctx->pagev[num_pages]);
+				block_ctx->pagev[num_pages] = NULL;
+			}
+		}
+
+		kfree(block_ctx->mem_to_free);
+		block_ctx->mem_to_free = NULL;
+		block_ctx->pagev = NULL;
+		block_ctx->datav = NULL;
+	}
+}
+
+static int btrfsic_read_block(struct btrfsic_state *state,
+			      struct btrfsic_block_data_ctx *block_ctx)
+{
+	unsigned int num_pages;
+	unsigned int i;
+	size_t size;
+	u64 dev_bytenr;
+	int ret;
+
+	BUG_ON(block_ctx->datav);
+	BUG_ON(block_ctx->pagev);
+	BUG_ON(block_ctx->mem_to_free);
+	if (!PAGE_ALIGNED(block_ctx->dev_bytenr)) {
+		pr_info("btrfsic: read_block() with unaligned bytenr %llu\n",
+		       block_ctx->dev_bytenr);
+		return -1;
+	}
+
+	num_pages = (block_ctx->len + (u64)PAGE_SIZE - 1) >>
+		    PAGE_SHIFT;
+	size = sizeof(*block_ctx->datav) + sizeof(*block_ctx->pagev);
+	block_ctx->mem_to_free = kcalloc(num_pages, size, GFP_NOFS);
+	if (!block_ctx->mem_to_free)
+		return -ENOMEM;
+	block_ctx->datav = block_ctx->mem_to_free;
+	block_ctx->pagev = (struct page **)(block_ctx->datav + num_pages);
+	for (i = 0; i < num_pages; i++) {
+		block_ctx->pagev[i] = alloc_page(GFP_NOFS);
+		if (!block_ctx->pagev[i])
+			return -1;
+	}
+
+	dev_bytenr = block_ctx->dev_bytenr;
+	for (i = 0; i < num_pages;) {
+		struct bio *bio;
+		unsigned int j;
+
+		bio = btrfs_io_bio_alloc(num_pages - i);
+		bio_set_dev(bio, block_ctx->dev->bdev);
+		bio->bi_iter.bi_sector = dev_bytenr >> 9;
+		bio->bi_opf = REQ_OP_READ;
+
+		for (j = i; j < num_pages; j++) {
+			ret = bio_add_page(bio, block_ctx->pagev[j],
+					   PAGE_SIZE, 0);
+			if (PAGE_SIZE != ret)
+				break;
+		}
+		if (j == i) {
+			pr_info("btrfsic: error, failed to add a single page!\n");
+			return -1;
+		}
+		if (submit_bio_wait(bio)) {
+			pr_info("btrfsic: read error at logical %llu dev %s!\n",
+			       block_ctx->start, block_ctx->dev->name);
+			bio_put(bio);
+			return -1;
+		}
+		bio_put(bio);
+		dev_bytenr += (j - i) * PAGE_SIZE;
+		i = j;
+	}
+	for (i = 0; i < num_pages; i++)
+		block_ctx->datav[i] = kmap(block_ctx->pagev[i]);
+
+	return block_ctx->len;
+}
+
+static void btrfsic_dump_database(struct btrfsic_state *state)
+{
+	const struct btrfsic_block *b_all;
+
+	BUG_ON(NULL == state);
+
+	pr_info("all_blocks_list:\n");
+	list_for_each_entry(b_all, &state->all_blocks_list, all_blocks_node) {
+		const struct btrfsic_block_link *l;
+
+		pr_info("%c-block @%llu (%s/%llu/%d)\n",
+		       btrfsic_get_block_type(state, b_all),
+		       b_all->logical_bytenr, b_all->dev_state->name,
+		       b_all->dev_bytenr, b_all->mirror_num);
+
+		list_for_each_entry(l, &b_all->ref_to_list, node_ref_to) {
+			pr_info(" %c @%llu (%s/%llu/%d) refers %u* to %c @%llu (%s/%llu/%d)\n",
+			       btrfsic_get_block_type(state, b_all),
+			       b_all->logical_bytenr, b_all->dev_state->name,
+			       b_all->dev_bytenr, b_all->mirror_num,
+			       l->ref_cnt,
+			       btrfsic_get_block_type(state, l->block_ref_to),
+			       l->block_ref_to->logical_bytenr,
+			       l->block_ref_to->dev_state->name,
+			       l->block_ref_to->dev_bytenr,
+			       l->block_ref_to->mirror_num);
+		}
+
+		list_for_each_entry(l, &b_all->ref_from_list, node_ref_from) {
+			pr_info(" %c @%llu (%s/%llu/%d) is ref %u* from %c @%llu (%s/%llu/%d)\n",
+			       btrfsic_get_block_type(state, b_all),
+			       b_all->logical_bytenr, b_all->dev_state->name,
+			       b_all->dev_bytenr, b_all->mirror_num,
+			       l->ref_cnt,
+			       btrfsic_get_block_type(state, l->block_ref_from),
+			       l->block_ref_from->logical_bytenr,
+			       l->block_ref_from->dev_state->name,
+			       l->block_ref_from->dev_bytenr,
+			       l->block_ref_from->mirror_num);
+		}
+
+		pr_info("\n");
+	}
+}
+
+/*
+ * Test whether the disk block contains a tree block (leaf or node)
+ * (note that this test fails for the super block)
+ */
+static noinline_for_stack int btrfsic_test_for_metadata(
+		struct btrfsic_state *state,
+		char **datav, unsigned int num_pages)
+{
+	struct btrfs_fs_info *fs_info = state->fs_info;
+	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
+	struct btrfs_header *h;
+	u8 csum[BTRFS_CSUM_SIZE];
+	unsigned int i;
+
+	if (num_pages * PAGE_SIZE < state->metablock_size)
+		return 1; /* not metadata */
+	num_pages = state->metablock_size >> PAGE_SHIFT;
+	h = (struct btrfs_header *)datav[0];
+
+	if (memcmp(h->fsid, fs_info->fs_devices->fsid, BTRFS_FSID_SIZE))
+		return 1;
+
+	shash->tfm = fs_info->csum_shash;
+	crypto_shash_init(shash);
+
+	for (i = 0; i < num_pages; i++) {
+		u8 *data = i ? datav[i] : (datav[i] + BTRFS_CSUM_SIZE);
+		size_t sublen = i ? PAGE_SIZE :
+				    (PAGE_SIZE - BTRFS_CSUM_SIZE);
+
+		crypto_shash_update(shash, data, sublen);
+	}
+	crypto_shash_final(shash, csum);
+	if (memcmp(csum, h->csum, state->csum_size))
+		return 1;
+
+	return 0; /* is metadata */
+}
+
+static void btrfsic_process_written_block(struct btrfsic_dev_state *dev_state,
+					  u64 dev_bytenr, char **mapped_datav,
+					  unsigned int num_pages,
+					  struct bio *bio, int *bio_is_patched,
+					  int submit_bio_bh_rw)
+{
+	int is_metadata;
+	struct btrfsic_block *block;
+	struct btrfsic_block_data_ctx block_ctx;
+	int ret;
+	struct btrfsic_state *state = dev_state->state;
+	struct block_device *bdev = dev_state->bdev;
+	unsigned int processed_len;
+
+	if (NULL != bio_is_patched)
+		*bio_is_patched = 0;
+
+again:
+	if (num_pages == 0)
+		return;
+
+	processed_len = 0;
+	is_metadata = (0 == btrfsic_test_for_metadata(state, mapped_datav,
+						      num_pages));
+
+	block = btrfsic_block_hashtable_lookup(bdev, dev_bytenr,
+					       &state->block_hashtable);
+	if (NULL != block) {
+		u64 bytenr = 0;
+		struct btrfsic_block_link *l, *tmp;
+
+		if (block->is_superblock) {
+			bytenr = btrfs_super_bytenr((struct btrfs_super_block *)
+						    mapped_datav[0]);
+			if (num_pages * PAGE_SIZE <
+			    BTRFS_SUPER_INFO_SIZE) {
+				pr_info("btrfsic: cannot work with too short bios!\n");
+				return;
+			}
+			is_metadata = 1;
+			BUG_ON(!PAGE_ALIGNED(BTRFS_SUPER_INFO_SIZE));
+			processed_len = BTRFS_SUPER_INFO_SIZE;
+			if (state->print_mask &
+			    BTRFSIC_PRINT_MASK_TREE_BEFORE_SB_WRITE) {
+				pr_info("[before new superblock is written]:\n");
+				btrfsic_dump_tree_sub(state, block, 0);
+			}
+		}
+		if (is_metadata) {
+			if (!block->is_superblock) {
+				if (num_pages * PAGE_SIZE <
+				    state->metablock_size) {
+					pr_info("btrfsic: cannot work with too short bios!\n");
+					return;
+				}
+				processed_len = state->metablock_size;
+				bytenr = btrfs_stack_header_bytenr(
+						(struct btrfs_header *)
+						mapped_datav[0]);
+				btrfsic_cmp_log_and_dev_bytenr(state, bytenr,
+							       dev_state,
+							       dev_bytenr);
+			}
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE) {
+				if (block->logical_bytenr != bytenr &&
+				    !(!block->is_metadata &&
+				      block->logical_bytenr == 0))
+					pr_info("Written block @%llu (%s/%llu/%d) found in hash table, %c, bytenr mismatch (!= stored %llu).\n",
+					       bytenr, dev_state->name,
+					       dev_bytenr,
+					       block->mirror_num,
+					       btrfsic_get_block_type(state,
+								      block),
+					       block->logical_bytenr);
+				else
+					pr_info("Written block @%llu (%s/%llu/%d) found in hash table, %c.\n",
+					       bytenr, dev_state->name,
+					       dev_bytenr, block->mirror_num,
+					       btrfsic_get_block_type(state,
+								      block));
+			}
+			block->logical_bytenr = bytenr;
+		} else {
+			if (num_pages * PAGE_SIZE <
+			    state->datablock_size) {
+				pr_info("btrfsic: cannot work with too short bios!\n");
+				return;
+			}
+			processed_len = state->datablock_size;
+			bytenr = block->logical_bytenr;
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+				pr_info("Written block @%llu (%s/%llu/%d) found in hash table, %c.\n",
+				       bytenr, dev_state->name, dev_bytenr,
+				       block->mirror_num,
+				       btrfsic_get_block_type(state, block));
+		}
+
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+			pr_info("ref_to_list: %cE, ref_from_list: %cE\n",
+			       list_empty(&block->ref_to_list) ? ' ' : '!',
+			       list_empty(&block->ref_from_list) ? ' ' : '!');
+		if (btrfsic_is_block_ref_by_superblock(state, block, 0)) {
+			pr_info("btrfs: attempt to overwrite %c-block @%llu (%s/%llu/%d), old(gen=%llu, objectid=%llu, type=%d, offset=%llu), new(gen=%llu), which is referenced by most recent superblock (superblockgen=%llu)!\n",
+			       btrfsic_get_block_type(state, block), bytenr,
+			       dev_state->name, dev_bytenr, block->mirror_num,
+			       block->generation,
+			       btrfs_disk_key_objectid(&block->disk_key),
+			       block->disk_key.type,
+			       btrfs_disk_key_offset(&block->disk_key),
+			       btrfs_stack_header_generation(
+				       (struct btrfs_header *) mapped_datav[0]),
+			       state->max_superblock_generation);
+			btrfsic_dump_tree(state);
+		}
+
+		if (!block->is_iodone && !block->never_written) {
+			pr_info("btrfs: attempt to overwrite %c-block @%llu (%s/%llu/%d), oldgen=%llu, newgen=%llu, which is not yet iodone!\n",
+			       btrfsic_get_block_type(state, block), bytenr,
+			       dev_state->name, dev_bytenr, block->mirror_num,
+			       block->generation,
+			       btrfs_stack_header_generation(
+				       (struct btrfs_header *)
+				       mapped_datav[0]));
+			/* it would not be safe to go on */
+			btrfsic_dump_tree(state);
+			goto continue_loop;
+		}
+
+		/*
+		 * Clear all references of this block. Do not free
+		 * the block itself even if is not referenced anymore
+		 * because it still carries valuable information
+		 * like whether it was ever written and IO completed.
+		 */
+		list_for_each_entry_safe(l, tmp, &block->ref_to_list,
+					 node_ref_to) {
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+				btrfsic_print_rem_link(state, l);
+			l->ref_cnt--;
+			if (0 == l->ref_cnt) {
+				list_del(&l->node_ref_to);
+				list_del(&l->node_ref_from);
+				btrfsic_block_link_hashtable_remove(l);
+				btrfsic_block_link_free(l);
+			}
+		}
+
+		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;
+			block->iodone_w_error = 0;
+			if (NULL != bio) {
+				block->is_iodone = 0;
+				BUG_ON(NULL == bio_is_patched);
+				if (!*bio_is_patched) {
+					block->orig_bio_private =
+					    bio->bi_private;
+					block->orig_bio_end_io =
+					    bio->bi_end_io;
+					block->next_in_same_bio = NULL;
+					bio->bi_private = block;
+					bio->bi_end_io = btrfsic_bio_end_io;
+					*bio_is_patched = 1;
+				} else {
+					struct btrfsic_block *chained_block =
+					    (struct btrfsic_block *)
+					    bio->bi_private;
+
+					BUG_ON(NULL == chained_block);
+					block->orig_bio_private =
+					    chained_block->orig_bio_private;
+					block->orig_bio_end_io =
+					    chained_block->orig_bio_end_io;
+					block->next_in_same_bio = chained_block;
+					bio->bi_private = block;
+				}
+			} else {
+				block->is_iodone = 1;
+				block->orig_bio_private = NULL;
+				block->orig_bio_end_io = NULL;
+				block->next_in_same_bio = NULL;
+			}
+		}
+
+		block->flush_gen = dev_state->last_flush_gen + 1;
+		block->submit_bio_bh_rw = submit_bio_bh_rw;
+		if (is_metadata) {
+			block->logical_bytenr = bytenr;
+			block->is_metadata = 1;
+			if (block->is_superblock) {
+				BUG_ON(PAGE_SIZE !=
+				       BTRFS_SUPER_INFO_SIZE);
+				ret = btrfsic_process_written_superblock(
+						state,
+						block,
+						(struct btrfs_super_block *)
+						mapped_datav[0]);
+				if (state->print_mask &
+				    BTRFSIC_PRINT_MASK_TREE_AFTER_SB_WRITE) {
+					pr_info("[after new superblock is written]:\n");
+					btrfsic_dump_tree_sub(state, block, 0);
+				}
+			} else {
+				block->mirror_num = 0;	/* unknown */
+				ret = btrfsic_process_metablock(
+						state,
+						block,
+						&block_ctx,
+						0, 0);
+			}
+			if (ret)
+				pr_info("btrfsic: btrfsic_process_metablock(root @%llu) failed!\n",
+				       dev_bytenr);
+		} else {
+			block->is_metadata = 0;
+			block->mirror_num = 0;	/* unknown */
+			block->generation = BTRFSIC_GENERATION_UNKNOWN;
+			if (!state->include_extent_data
+			    && list_empty(&block->ref_from_list)) {
+				/*
+				 * disk block is overwritten with extent
+				 * data (not meta data) and we are configured
+				 * to not include extent data: take the
+				 * chance and free the block's memory
+				 */
+				btrfsic_block_hashtable_remove(block);
+				list_del(&block->all_blocks_node);
+				btrfsic_block_free(block);
+			}
+		}
+		btrfsic_release_block_ctx(&block_ctx);
+	} else {
+		/* block has not been found in hash table */
+		u64 bytenr;
+
+		if (!is_metadata) {
+			processed_len = state->datablock_size;
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+				pr_info("Written block (%s/%llu/?) !found in hash table, D.\n",
+				       dev_state->name, dev_bytenr);
+			if (!state->include_extent_data) {
+				/* ignore that written D block */
+				goto continue_loop;
+			}
+
+			/* this is getting ugly for the
+			 * include_extent_data case... */
+			bytenr = 0;	/* unknown */
+		} else {
+			processed_len = state->metablock_size;
+			bytenr = btrfs_stack_header_bytenr(
+					(struct btrfs_header *)
+					mapped_datav[0]);
+			btrfsic_cmp_log_and_dev_bytenr(state, bytenr, dev_state,
+						       dev_bytenr);
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+				pr_info("Written block @%llu (%s/%llu/?) !found in hash table, M.\n",
+				       bytenr, dev_state->name, dev_bytenr);
+		}
+
+		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) {
+			btrfsic_release_block_ctx(&block_ctx);
+			goto continue_loop;
+		}
+		block->dev_state = dev_state;
+		block->dev_bytenr = dev_bytenr;
+		block->logical_bytenr = bytenr;
+		block->is_metadata = is_metadata;
+		block->never_written = 0;
+		block->iodone_w_error = 0;
+		block->mirror_num = 0;	/* unknown */
+		block->flush_gen = dev_state->last_flush_gen + 1;
+		block->submit_bio_bh_rw = submit_bio_bh_rw;
+		if (NULL != bio) {
+			block->is_iodone = 0;
+			BUG_ON(NULL == bio_is_patched);
+			if (!*bio_is_patched) {
+				block->orig_bio_private = bio->bi_private;
+				block->orig_bio_end_io = bio->bi_end_io;
+				block->next_in_same_bio = NULL;
+				bio->bi_private = block;
+				bio->bi_end_io = btrfsic_bio_end_io;
+				*bio_is_patched = 1;
+			} else {
+				struct btrfsic_block *chained_block =
+				    (struct btrfsic_block *)
+				    bio->bi_private;
+
+				BUG_ON(NULL == chained_block);
+				block->orig_bio_private =
+				    chained_block->orig_bio_private;
+				block->orig_bio_end_io =
+				    chained_block->orig_bio_end_io;
+				block->next_in_same_bio = chained_block;
+				bio->bi_private = block;
+			}
+		} else {
+			block->is_iodone = 1;
+			block->orig_bio_private = NULL;
+			block->orig_bio_end_io = NULL;
+			block->next_in_same_bio = NULL;
+		}
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+			pr_info("New written %c-block @%llu (%s/%llu/%d)\n",
+			       is_metadata ? 'M' : 'D',
+			       block->logical_bytenr, block->dev_state->name,
+			       block->dev_bytenr, block->mirror_num);
+		list_add(&block->all_blocks_node, &state->all_blocks_list);
+		btrfsic_block_hashtable_add(block, &state->block_hashtable);
+
+		if (is_metadata) {
+			ret = btrfsic_process_metablock(state, block,
+							&block_ctx, 0, 0);
+			if (ret)
+				pr_info("btrfsic: process_metablock(root @%llu) failed!\n",
+				       dev_bytenr);
+		}
+		btrfsic_release_block_ctx(&block_ctx);
+	}
+
+continue_loop:
+	BUG_ON(!processed_len);
+	dev_bytenr += processed_len;
+	mapped_datav += processed_len >> PAGE_SHIFT;
+	num_pages -= processed_len >> PAGE_SHIFT;
+	goto again;
+}
+
+static void btrfsic_bio_end_io(struct bio *bp)
+{
+	struct btrfsic_block *block = (struct btrfsic_block *)bp->bi_private;
+	int iodone_w_error;
+
+	/* mutex is not held! This is not save if IO is not yet completed
+	 * on umount */
+	iodone_w_error = 0;
+	if (bp->bi_status)
+		iodone_w_error = 1;
+
+	BUG_ON(NULL == block);
+	bp->bi_private = block->orig_bio_private;
+	bp->bi_end_io = block->orig_bio_end_io;
+
+	do {
+		struct btrfsic_block *next_block;
+		struct btrfsic_dev_state *const dev_state = block->dev_state;
+
+		if ((dev_state->state->print_mask &
+		     BTRFSIC_PRINT_MASK_END_IO_BIO_BH))
+			pr_info("bio_end_io(err=%d) for %c @%llu (%s/%llu/%d)\n",
+			       bp->bi_status,
+			       btrfsic_get_block_type(dev_state->state, block),
+			       block->logical_bytenr, dev_state->name,
+			       block->dev_bytenr, block->mirror_num);
+		next_block = block->next_in_same_bio;
+		block->iodone_w_error = iodone_w_error;
+		if (block->submit_bio_bh_rw & REQ_PREFLUSH) {
+			dev_state->last_flush_gen++;
+			if ((dev_state->state->print_mask &
+			     BTRFSIC_PRINT_MASK_END_IO_BIO_BH))
+				pr_info("bio_end_io() new %s flush_gen=%llu\n",
+				       dev_state->name,
+				       dev_state->last_flush_gen);
+		}
+		if (block->submit_bio_bh_rw & REQ_FUA)
+			block->flush_gen = 0; /* FUA completed means block is
+					       * on disk */
+		block->is_iodone = 1; /* for FLUSH, this releases the block */
+		block = next_block;
+	} while (NULL != block);
+
+	bp->bi_end_io(bp);
+}
+
+static int btrfsic_process_written_superblock(
+		struct btrfsic_state *state,
+		struct btrfsic_block *const superblock,
+		struct btrfs_super_block *const super_hdr)
+{
+	struct btrfs_fs_info *fs_info = state->fs_info;
+	int pass;
+
+	superblock->generation = btrfs_super_generation(super_hdr);
+	if (!(superblock->generation > state->max_superblock_generation ||
+	      0 == state->max_superblock_generation)) {
+		if (state->print_mask & BTRFSIC_PRINT_MASK_SUPERBLOCK_WRITE)
+			pr_info("btrfsic: superblock @%llu (%s/%llu/%d) with old gen %llu <= %llu\n",
+			       superblock->logical_bytenr,
+			       superblock->dev_state->name,
+			       superblock->dev_bytenr, superblock->mirror_num,
+			       btrfs_super_generation(super_hdr),
+			       state->max_superblock_generation);
+	} else {
+		if (state->print_mask & BTRFSIC_PRINT_MASK_SUPERBLOCK_WRITE)
+			pr_info("btrfsic: got new superblock @%llu (%s/%llu/%d) with new gen %llu > %llu\n",
+			       superblock->logical_bytenr,
+			       superblock->dev_state->name,
+			       superblock->dev_bytenr, superblock->mirror_num,
+			       btrfs_super_generation(super_hdr),
+			       state->max_superblock_generation);
+
+		state->max_superblock_generation =
+		    btrfs_super_generation(super_hdr);
+		state->latest_superblock = superblock;
+	}
+
+	for (pass = 0; pass < 3; pass++) {
+		int ret;
+		u64 next_bytenr;
+		struct btrfsic_block *next_block;
+		struct btrfsic_block_data_ctx tmp_next_block_ctx;
+		struct btrfsic_block_link *l;
+		int num_copies;
+		int mirror_num;
+		const char *additional_string = NULL;
+		struct btrfs_disk_key tmp_disk_key = {0};
+
+		btrfs_set_disk_key_objectid(&tmp_disk_key,
+					    BTRFS_ROOT_ITEM_KEY);
+		btrfs_set_disk_key_objectid(&tmp_disk_key, 0);
+
+		switch (pass) {
+		case 0:
+			btrfs_set_disk_key_objectid(&tmp_disk_key,
+						    BTRFS_ROOT_TREE_OBJECTID);
+			additional_string = "root ";
+			next_bytenr = btrfs_super_root(super_hdr);
+			if (state->print_mask &
+			    BTRFSIC_PRINT_MASK_ROOT_CHUNK_LOG_TREE_LOCATION)
+				pr_info("root@%llu\n", next_bytenr);
+			break;
+		case 1:
+			btrfs_set_disk_key_objectid(&tmp_disk_key,
+						    BTRFS_CHUNK_TREE_OBJECTID);
+			additional_string = "chunk ";
+			next_bytenr = btrfs_super_chunk_root(super_hdr);
+			if (state->print_mask &
+			    BTRFSIC_PRINT_MASK_ROOT_CHUNK_LOG_TREE_LOCATION)
+				pr_info("chunk@%llu\n", next_bytenr);
+			break;
+		case 2:
+			btrfs_set_disk_key_objectid(&tmp_disk_key,
+						    BTRFS_TREE_LOG_OBJECTID);
+			additional_string = "log ";
+			next_bytenr = btrfs_super_log_root(super_hdr);
+			if (0 == next_bytenr)
+				continue;
+			if (state->print_mask &
+			    BTRFSIC_PRINT_MASK_ROOT_CHUNK_LOG_TREE_LOCATION)
+				pr_info("log@%llu\n", next_bytenr);
+			break;
+		}
+
+		num_copies = btrfs_num_copies(fs_info, next_bytenr,
+					      BTRFS_SUPER_INFO_SIZE);
+		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
+			pr_info("num_copies(log_bytenr=%llu) = %d\n",
+			       next_bytenr, num_copies);
+		for (mirror_num = 1; mirror_num <= num_copies; mirror_num++) {
+			int was_created;
+
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+				pr_info("btrfsic_process_written_superblock(mirror_num=%d)\n", mirror_num);
+			ret = btrfsic_map_block(state, next_bytenr,
+						BTRFS_SUPER_INFO_SIZE,
+						&tmp_next_block_ctx,
+						mirror_num);
+			if (ret) {
+				pr_info("btrfsic: btrfsic_map_block(@%llu, mirror=%d) failed!\n",
+				       next_bytenr, mirror_num);
+				return -1;
+			}
+
+			next_block = btrfsic_block_lookup_or_add(
+					state,
+					&tmp_next_block_ctx,
+					additional_string,
+					1, 0, 1,
+					mirror_num,
+					&was_created);
+			if (NULL == next_block) {
+				btrfsic_release_block_ctx(&tmp_next_block_ctx);
+				return -1;
+			}
+
+			next_block->disk_key = tmp_disk_key;
+			if (was_created)
+				next_block->generation =
+				    BTRFSIC_GENERATION_UNKNOWN;
+			l = btrfsic_block_link_lookup_or_add(
+					state,
+					&tmp_next_block_ctx,
+					next_block,
+					superblock,
+					BTRFSIC_GENERATION_UNKNOWN);
+			btrfsic_release_block_ctx(&tmp_next_block_ctx);
+			if (NULL == l)
+				return -1;
+		}
+	}
+
+	if (WARN_ON(-1 == btrfsic_check_all_ref_blocks(state, superblock, 0)))
+		btrfsic_dump_tree(state);
+
+	return 0;
+}
+
+static int btrfsic_check_all_ref_blocks(struct btrfsic_state *state,
+					struct btrfsic_block *const block,
+					int recursion_level)
+{
+	const struct btrfsic_block_link *l;
+	int ret = 0;
+
+	if (recursion_level >= 3 + BTRFS_MAX_LEVEL) {
+		/*
+		 * Note that this situation can happen and does not
+		 * indicate an error in regular cases. It happens
+		 * when disk blocks are freed and later reused.
+		 * The check-integrity module is not aware of any
+		 * block free operations, it just recognizes block
+		 * write operations. Therefore it keeps the linkage
+		 * information for a block until a block is
+		 * rewritten. This can temporarily cause incorrect
+		 * and even circular linkage information. This
+		 * causes no harm unless such blocks are referenced
+		 * by the most recent super block.
+		 */
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+			pr_info("btrfsic: abort cyclic linkage (case 1).\n");
+
+		return ret;
+	}
+
+	/*
+	 * This algorithm is recursive because the amount of used stack
+	 * space is very small and the max recursion depth is limited.
+	 */
+	list_for_each_entry(l, &block->ref_to_list, node_ref_to) {
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+			pr_info("rl=%d, %c @%llu (%s/%llu/%d) %u* refers to %c @%llu (%s/%llu/%d)\n",
+			       recursion_level,
+			       btrfsic_get_block_type(state, block),
+			       block->logical_bytenr, block->dev_state->name,
+			       block->dev_bytenr, block->mirror_num,
+			       l->ref_cnt,
+			       btrfsic_get_block_type(state, l->block_ref_to),
+			       l->block_ref_to->logical_bytenr,
+			       l->block_ref_to->dev_state->name,
+			       l->block_ref_to->dev_bytenr,
+			       l->block_ref_to->mirror_num);
+		if (l->block_ref_to->never_written) {
+			pr_info("btrfs: attempt to write superblock which references block %c @%llu (%s/%llu/%d) which is never written!\n",
+			       btrfsic_get_block_type(state, l->block_ref_to),
+			       l->block_ref_to->logical_bytenr,
+			       l->block_ref_to->dev_state->name,
+			       l->block_ref_to->dev_bytenr,
+			       l->block_ref_to->mirror_num);
+			ret = -1;
+		} else if (!l->block_ref_to->is_iodone) {
+			pr_info("btrfs: attempt to write superblock which references block %c @%llu (%s/%llu/%d) which is not yet iodone!\n",
+			       btrfsic_get_block_type(state, l->block_ref_to),
+			       l->block_ref_to->logical_bytenr,
+			       l->block_ref_to->dev_state->name,
+			       l->block_ref_to->dev_bytenr,
+			       l->block_ref_to->mirror_num);
+			ret = -1;
+		} else if (l->block_ref_to->iodone_w_error) {
+			pr_info("btrfs: attempt to write superblock which references block %c @%llu (%s/%llu/%d) which has write error!\n",
+			       btrfsic_get_block_type(state, l->block_ref_to),
+			       l->block_ref_to->logical_bytenr,
+			       l->block_ref_to->dev_state->name,
+			       l->block_ref_to->dev_bytenr,
+			       l->block_ref_to->mirror_num);
+			ret = -1;
+		} else if (l->parent_generation !=
+			   l->block_ref_to->generation &&
+			   BTRFSIC_GENERATION_UNKNOWN !=
+			   l->parent_generation &&
+			   BTRFSIC_GENERATION_UNKNOWN !=
+			   l->block_ref_to->generation) {
+			pr_info("btrfs: attempt to write superblock which references block %c @%llu (%s/%llu/%d) with generation %llu != parent generation %llu!\n",
+			       btrfsic_get_block_type(state, l->block_ref_to),
+			       l->block_ref_to->logical_bytenr,
+			       l->block_ref_to->dev_state->name,
+			       l->block_ref_to->dev_bytenr,
+			       l->block_ref_to->mirror_num,
+			       l->block_ref_to->generation,
+			       l->parent_generation);
+			ret = -1;
+		} else if (l->block_ref_to->flush_gen >
+			   l->block_ref_to->dev_state->last_flush_gen) {
+			pr_info("btrfs: attempt to write superblock which references block %c @%llu (%s/%llu/%d) which is not flushed out of disk's write cache (block flush_gen=%llu, dev->flush_gen=%llu)!\n",
+			       btrfsic_get_block_type(state, l->block_ref_to),
+			       l->block_ref_to->logical_bytenr,
+			       l->block_ref_to->dev_state->name,
+			       l->block_ref_to->dev_bytenr,
+			       l->block_ref_to->mirror_num, block->flush_gen,
+			       l->block_ref_to->dev_state->last_flush_gen);
+			ret = -1;
+		} else if (-1 == btrfsic_check_all_ref_blocks(state,
+							      l->block_ref_to,
+							      recursion_level +
+							      1)) {
+			ret = -1;
+		}
+	}
+
+	return ret;
+}
+
+static int btrfsic_is_block_ref_by_superblock(
+		const struct btrfsic_state *state,
+		const struct btrfsic_block *block,
+		int recursion_level)
+{
+	const struct btrfsic_block_link *l;
+
+	if (recursion_level >= 3 + BTRFS_MAX_LEVEL) {
+		/* refer to comment at "abort cyclic linkage (case 1)" */
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+			pr_info("btrfsic: abort cyclic linkage (case 2).\n");
+
+		return 0;
+	}
+
+	/*
+	 * This algorithm is recursive because the amount of used stack space
+	 * is very small and the max recursion depth is limited.
+	 */
+	list_for_each_entry(l, &block->ref_from_list, node_ref_from) {
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+			pr_info("rl=%d, %c @%llu (%s/%llu/%d) is ref %u* from %c @%llu (%s/%llu/%d)\n",
+			       recursion_level,
+			       btrfsic_get_block_type(state, block),
+			       block->logical_bytenr, block->dev_state->name,
+			       block->dev_bytenr, block->mirror_num,
+			       l->ref_cnt,
+			       btrfsic_get_block_type(state, l->block_ref_from),
+			       l->block_ref_from->logical_bytenr,
+			       l->block_ref_from->dev_state->name,
+			       l->block_ref_from->dev_bytenr,
+			       l->block_ref_from->mirror_num);
+		if (l->block_ref_from->is_superblock &&
+		    state->latest_superblock->dev_bytenr ==
+		    l->block_ref_from->dev_bytenr &&
+		    state->latest_superblock->dev_state->bdev ==
+		    l->block_ref_from->dev_state->bdev)
+			return 1;
+		else if (btrfsic_is_block_ref_by_superblock(state,
+							    l->block_ref_from,
+							    recursion_level +
+							    1))
+			return 1;
+	}
+
+	return 0;
+}
+
+static void btrfsic_print_add_link(const struct btrfsic_state *state,
+				   const struct btrfsic_block_link *l)
+{
+	pr_info("Add %u* link from %c @%llu (%s/%llu/%d) to %c @%llu (%s/%llu/%d).\n",
+	       l->ref_cnt,
+	       btrfsic_get_block_type(state, l->block_ref_from),
+	       l->block_ref_from->logical_bytenr,
+	       l->block_ref_from->dev_state->name,
+	       l->block_ref_from->dev_bytenr, l->block_ref_from->mirror_num,
+	       btrfsic_get_block_type(state, l->block_ref_to),
+	       l->block_ref_to->logical_bytenr,
+	       l->block_ref_to->dev_state->name, l->block_ref_to->dev_bytenr,
+	       l->block_ref_to->mirror_num);
+}
+
+static void btrfsic_print_rem_link(const struct btrfsic_state *state,
+				   const struct btrfsic_block_link *l)
+{
+	pr_info("Rem %u* link from %c @%llu (%s/%llu/%d) to %c @%llu (%s/%llu/%d).\n",
+	       l->ref_cnt,
+	       btrfsic_get_block_type(state, l->block_ref_from),
+	       l->block_ref_from->logical_bytenr,
+	       l->block_ref_from->dev_state->name,
+	       l->block_ref_from->dev_bytenr, l->block_ref_from->mirror_num,
+	       btrfsic_get_block_type(state, l->block_ref_to),
+	       l->block_ref_to->logical_bytenr,
+	       l->block_ref_to->dev_state->name, l->block_ref_to->dev_bytenr,
+	       l->block_ref_to->mirror_num);
+}
+
+static char btrfsic_get_block_type(const struct btrfsic_state *state,
+				   const struct btrfsic_block *block)
+{
+	if (block->is_superblock &&
+	    state->latest_superblock->dev_bytenr == block->dev_bytenr &&
+	    state->latest_superblock->dev_state->bdev == block->dev_state->bdev)
+		return 'S';
+	else if (block->is_superblock)
+		return 's';
+	else if (block->is_metadata)
+		return 'M';
+	else
+		return 'D';
+}
+
+static void btrfsic_dump_tree(const struct btrfsic_state *state)
+{
+	btrfsic_dump_tree_sub(state, state->latest_superblock, 0);
+}
+
+static void btrfsic_dump_tree_sub(const struct btrfsic_state *state,
+				  const struct btrfsic_block *block,
+				  int indent_level)
+{
+	const struct btrfsic_block_link *l;
+	int indent_add;
+	static char buf[80];
+	int cursor_position;
+
+	/*
+	 * Should better fill an on-stack buffer with a complete line and
+	 * dump it at once when it is time to print a newline character.
+	 */
+
+	/*
+	 * This algorithm is recursive because the amount of used stack space
+	 * is very small and the max recursion depth is limited.
+	 */
+	indent_add = sprintf(buf, "%c-%llu(%s/%llu/%u)",
+			     btrfsic_get_block_type(state, block),
+			     block->logical_bytenr, block->dev_state->name,
+			     block->dev_bytenr, block->mirror_num);
+	if (indent_level + indent_add > BTRFSIC_TREE_DUMP_MAX_INDENT_LEVEL) {
+		printk("[...]\n");
+		return;
+	}
+	printk(buf);
+	indent_level += indent_add;
+	if (list_empty(&block->ref_to_list)) {
+		printk("\n");
+		return;
+	}
+	if (block->mirror_num > 1 &&
+	    !(state->print_mask & BTRFSIC_PRINT_MASK_TREE_WITH_ALL_MIRRORS)) {
+		printk(" [...]\n");
+		return;
+	}
+
+	cursor_position = indent_level;
+	list_for_each_entry(l, &block->ref_to_list, node_ref_to) {
+		while (cursor_position < indent_level) {
+			printk(" ");
+			cursor_position++;
+		}
+		if (l->ref_cnt > 1)
+			indent_add = sprintf(buf, " %d*--> ", l->ref_cnt);
+		else
+			indent_add = sprintf(buf, " --> ");
+		if (indent_level + indent_add >
+		    BTRFSIC_TREE_DUMP_MAX_INDENT_LEVEL) {
+			printk("[...]\n");
+			cursor_position = 0;
+			continue;
+		}
+
+		printk(buf);
+
+		btrfsic_dump_tree_sub(state, l->block_ref_to,
+				      indent_level + indent_add);
+		cursor_position = 0;
+	}
+}
+
+static struct btrfsic_block_link *btrfsic_block_link_lookup_or_add(
+		struct btrfsic_state *state,
+		struct btrfsic_block_data_ctx *next_block_ctx,
+		struct btrfsic_block *next_block,
+		struct btrfsic_block *from_block,
+		u64 parent_generation)
+{
+	struct btrfsic_block_link *l;
+
+	l = btrfsic_block_link_hashtable_lookup(next_block_ctx->dev->bdev,
+						next_block_ctx->dev_bytenr,
+						from_block->dev_state->bdev,
+						from_block->dev_bytenr,
+						&state->block_link_hashtable);
+	if (NULL == l) {
+		l = btrfsic_block_link_alloc();
+		if (!l)
+			return NULL;
+
+		l->block_ref_to = next_block;
+		l->block_ref_from = from_block;
+		l->ref_cnt = 1;
+		l->parent_generation = parent_generation;
+
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+			btrfsic_print_add_link(state, l);
+
+		list_add(&l->node_ref_to, &from_block->ref_to_list);
+		list_add(&l->node_ref_from, &next_block->ref_from_list);
+
+		btrfsic_block_link_hashtable_add(l,
+						 &state->block_link_hashtable);
+	} else {
+		l->ref_cnt++;
+		l->parent_generation = parent_generation;
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+			btrfsic_print_add_link(state, l);
+	}
+
+	return l;
+}
+
+static struct btrfsic_block *btrfsic_block_lookup_or_add(
+		struct btrfsic_state *state,
+		struct btrfsic_block_data_ctx *block_ctx,
+		const char *additional_string,
+		int is_metadata,
+		int is_iodone,
+		int never_written,
+		int mirror_num,
+		int *was_created)
+{
+	struct btrfsic_block *block;
+
+	block = btrfsic_block_hashtable_lookup(block_ctx->dev->bdev,
+					       block_ctx->dev_bytenr,
+					       &state->block_hashtable);
+	if (NULL == block) {
+		struct btrfsic_dev_state *dev_state;
+
+		block = btrfsic_block_alloc();
+		if (!block)
+			return NULL;
+
+		dev_state = btrfsic_dev_state_lookup(block_ctx->dev->bdev->bd_dev);
+		if (NULL == dev_state) {
+			pr_info("btrfsic: error, lookup dev_state failed!\n");
+			btrfsic_block_free(block);
+			return NULL;
+		}
+		block->dev_state = dev_state;
+		block->dev_bytenr = block_ctx->dev_bytenr;
+		block->logical_bytenr = block_ctx->start;
+		block->is_metadata = is_metadata;
+		block->is_iodone = is_iodone;
+		block->never_written = never_written;
+		block->mirror_num = mirror_num;
+		if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+			pr_info("New %s%c-block @%llu (%s/%llu/%d)\n",
+			       additional_string,
+			       btrfsic_get_block_type(state, block),
+			       block->logical_bytenr, dev_state->name,
+			       block->dev_bytenr, mirror_num);
+		list_add(&block->all_blocks_node, &state->all_blocks_list);
+		btrfsic_block_hashtable_add(block, &state->block_hashtable);
+		if (NULL != was_created)
+			*was_created = 1;
+	} else {
+		if (NULL != was_created)
+			*was_created = 0;
+	}
+
+	return block;
+}
+
+static void btrfsic_cmp_log_and_dev_bytenr(struct btrfsic_state *state,
+					   u64 bytenr,
+					   struct btrfsic_dev_state *dev_state,
+					   u64 dev_bytenr)
+{
+	struct btrfs_fs_info *fs_info = state->fs_info;
+	struct btrfsic_block_data_ctx block_ctx;
+	int num_copies;
+	int mirror_num;
+	int match = 0;
+	int ret;
+
+	num_copies = btrfs_num_copies(fs_info, bytenr, state->metablock_size);
+
+	for (mirror_num = 1; mirror_num <= num_copies; mirror_num++) {
+		ret = btrfsic_map_block(state, bytenr, state->metablock_size,
+					&block_ctx, mirror_num);
+		if (ret) {
+			pr_info("btrfsic: btrfsic_map_block(logical @%llu, mirror %d) failed!\n",
+			       bytenr, mirror_num);
+			continue;
+		}
+
+		if (dev_state->bdev == block_ctx.dev->bdev &&
+		    dev_bytenr == block_ctx.dev_bytenr) {
+			match++;
+			btrfsic_release_block_ctx(&block_ctx);
+			break;
+		}
+		btrfsic_release_block_ctx(&block_ctx);
+	}
+
+	if (WARN_ON(!match)) {
+		pr_info("btrfs: attempt to write M-block which contains logical bytenr that doesn't map to dev+physical bytenr of submit_bio, buffer->log_bytenr=%llu, submit_bio(bdev=%s, phys_bytenr=%llu)!\n",
+		       bytenr, dev_state->name, dev_bytenr);
+		for (mirror_num = 1; mirror_num <= num_copies; mirror_num++) {
+			ret = btrfsic_map_block(state, bytenr,
+						state->metablock_size,
+						&block_ctx, mirror_num);
+			if (ret)
+				continue;
+
+			pr_info("Read logical bytenr @%llu maps to (%s/%llu/%d)\n",
+			       bytenr, block_ctx.dev->name,
+			       block_ctx.dev_bytenr, mirror_num);
+		}
+	}
+}
+
+static struct btrfsic_dev_state *btrfsic_dev_state_lookup(dev_t dev)
+{
+	return btrfsic_dev_state_hashtable_lookup(dev,
+						  &btrfsic_dev_state_hashtable);
+}
+
+static void __btrfsic_submit_bio(struct bio *bio)
+{
+	struct btrfsic_dev_state *dev_state;
+
+	if (!btrfsic_is_initialized)
+		return;
+
+	mutex_lock(&btrfsic_mutex);
+	/* since btrfsic_submit_bio() is also called before
+	 * btrfsic_mount(), this might return NULL */
+	dev_state = btrfsic_dev_state_lookup(bio_dev(bio) + bio->bi_partno);
+	if (NULL != dev_state &&
+	    (bio_op(bio) == REQ_OP_WRITE) && bio_has_data(bio)) {
+		unsigned int i = 0;
+		u64 dev_bytenr;
+		u64 cur_bytenr;
+		struct bio_vec bvec;
+		struct bvec_iter iter;
+		int bio_is_patched;
+		char **mapped_datav;
+		unsigned int segs = bio_segments(bio);
+
+		dev_bytenr = 512 * bio->bi_iter.bi_sector;
+		bio_is_patched = 0;
+		if (dev_state->state->print_mask &
+		    BTRFSIC_PRINT_MASK_SUBMIT_BIO_BH)
+			pr_info("submit_bio(rw=%d,0x%x, bi_vcnt=%u, bi_sector=%llu (bytenr %llu), bi_disk=%p)\n",
+			       bio_op(bio), bio->bi_opf, segs,
+			       (unsigned long long)bio->bi_iter.bi_sector,
+			       dev_bytenr, bio->bi_disk);
+
+		mapped_datav = kmalloc_array(segs,
+					     sizeof(*mapped_datav), GFP_NOFS);
+		if (!mapped_datav)
+			goto leave;
+		cur_bytenr = dev_bytenr;
+
+		bio_for_each_segment(bvec, bio, iter) {
+			BUG_ON(bvec.bv_len != PAGE_SIZE);
+			mapped_datav[i] = kmap(bvec.bv_page);
+			i++;
+
+			if (dev_state->state->print_mask &
+			    BTRFSIC_PRINT_MASK_SUBMIT_BIO_BH_VERBOSE)
+				pr_info("#%u: bytenr=%llu, len=%u, offset=%u\n",
+				       i, cur_bytenr, bvec.bv_len, bvec.bv_offset);
+			cur_bytenr += bvec.bv_len;
+		}
+		btrfsic_process_written_block(dev_state, dev_bytenr,
+					      mapped_datav, segs,
+					      bio, &bio_is_patched,
+					      bio->bi_opf);
+		bio_for_each_segment(bvec, bio, iter)
+			kunmap(bvec.bv_page);
+		kfree(mapped_datav);
+	} else if (NULL != dev_state && (bio->bi_opf & REQ_PREFLUSH)) {
+		if (dev_state->state->print_mask &
+		    BTRFSIC_PRINT_MASK_SUBMIT_BIO_BH)
+			pr_info("submit_bio(rw=%d,0x%x FLUSH, disk=%p)\n",
+			       bio_op(bio), bio->bi_opf, bio->bi_disk);
+		if (!dev_state->dummy_block_for_bio_bh_flush.is_iodone) {
+			if ((dev_state->state->print_mask &
+			     (BTRFSIC_PRINT_MASK_SUBMIT_BIO_BH |
+			      BTRFSIC_PRINT_MASK_VERBOSE)))
+				pr_info("btrfsic_submit_bio(%s) with FLUSH but dummy block already in use (ignored)!\n",
+				       dev_state->name);
+		} else {
+			struct btrfsic_block *const block =
+				&dev_state->dummy_block_for_bio_bh_flush;
+
+			block->is_iodone = 0;
+			block->never_written = 0;
+			block->iodone_w_error = 0;
+			block->flush_gen = dev_state->last_flush_gen + 1;
+			block->submit_bio_bh_rw = bio->bi_opf;
+			block->orig_bio_private = bio->bi_private;
+			block->orig_bio_end_io = bio->bi_end_io;
+			block->next_in_same_bio = NULL;
+			bio->bi_private = block;
+			bio->bi_end_io = btrfsic_bio_end_io;
+		}
+	}
+leave:
+	mutex_unlock(&btrfsic_mutex);
+}
+
+void btrfsic_submit_bio(struct bio *bio)
+{
+	__btrfsic_submit_bio(bio);
+	submit_bio(bio);
+}
+
+int btrfsic_submit_bio_wait(struct bio *bio)
+{
+	__btrfsic_submit_bio(bio);
+	return submit_bio_wait(bio);
+}
+
+int btrfsic_mount(struct btrfs_fs_info *fs_info,
+		  struct btrfs_fs_devices *fs_devices,
+		  int including_extent_data, u32 print_mask)
+{
+	int ret;
+	struct btrfsic_state *state;
+	struct list_head *dev_head = &fs_devices->devices;
+	struct btrfs_device *device;
+
+	if (!PAGE_ALIGNED(fs_info->nodesize)) {
+		pr_info("btrfsic: cannot handle nodesize %d not being a multiple of PAGE_SIZE %ld!\n",
+		       fs_info->nodesize, PAGE_SIZE);
+		return -1;
+	}
+	if (!PAGE_ALIGNED(fs_info->sectorsize)) {
+		pr_info("btrfsic: cannot handle sectorsize %d not being a multiple of PAGE_SIZE %ld!\n",
+		       fs_info->sectorsize, PAGE_SIZE);
+		return -1;
+	}
+	state = kvzalloc(sizeof(*state), GFP_KERNEL);
+	if (!state)
+		return -ENOMEM;
+
+	if (!btrfsic_is_initialized) {
+		mutex_init(&btrfsic_mutex);
+		btrfsic_dev_state_hashtable_init(&btrfsic_dev_state_hashtable);
+		btrfsic_is_initialized = 1;
+	}
+	mutex_lock(&btrfsic_mutex);
+	state->fs_info = fs_info;
+	state->print_mask = print_mask;
+	state->include_extent_data = including_extent_data;
+	state->csum_size = 0;
+	state->metablock_size = fs_info->nodesize;
+	state->datablock_size = fs_info->sectorsize;
+	INIT_LIST_HEAD(&state->all_blocks_list);
+	btrfsic_block_hashtable_init(&state->block_hashtable);
+	btrfsic_block_link_hashtable_init(&state->block_link_hashtable);
+	state->max_superblock_generation = 0;
+	state->latest_superblock = NULL;
+
+	list_for_each_entry(device, dev_head, dev_list) {
+		struct btrfsic_dev_state *ds;
+		const char *p;
+
+		if (!device->bdev || !device->name)
+			continue;
+
+		ds = btrfsic_dev_state_alloc();
+		if (NULL == ds) {
+			mutex_unlock(&btrfsic_mutex);
+			return -ENOMEM;
+		}
+		ds->bdev = device->bdev;
+		ds->state = state;
+		bdevname(ds->bdev, ds->name);
+		ds->name[BDEVNAME_SIZE - 1] = '\0';
+		p = kbasename(ds->name);
+		strlcpy(ds->name, p, sizeof(ds->name));
+		btrfsic_dev_state_hashtable_add(ds,
+						&btrfsic_dev_state_hashtable);
+	}
+
+	ret = btrfsic_process_superblock(state, fs_devices);
+	if (0 != ret) {
+		mutex_unlock(&btrfsic_mutex);
+		btrfsic_unmount(fs_devices);
+		return ret;
+	}
+
+	if (state->print_mask & BTRFSIC_PRINT_MASK_INITIAL_DATABASE)
+		btrfsic_dump_database(state);
+	if (state->print_mask & BTRFSIC_PRINT_MASK_INITIAL_TREE)
+		btrfsic_dump_tree(state);
+
+	mutex_unlock(&btrfsic_mutex);
+	return 0;
+}
+
+void btrfsic_unmount(struct btrfs_fs_devices *fs_devices)
+{
+	struct btrfsic_block *b_all, *tmp_all;
+	struct btrfsic_state *state;
+	struct list_head *dev_head = &fs_devices->devices;
+	struct btrfs_device *device;
+
+	if (!btrfsic_is_initialized)
+		return;
+
+	mutex_lock(&btrfsic_mutex);
+
+	state = NULL;
+	list_for_each_entry(device, dev_head, dev_list) {
+		struct btrfsic_dev_state *ds;
+
+		if (!device->bdev || !device->name)
+			continue;
+
+		ds = btrfsic_dev_state_hashtable_lookup(
+				device->bdev->bd_dev,
+				&btrfsic_dev_state_hashtable);
+		if (NULL != ds) {
+			state = ds->state;
+			btrfsic_dev_state_hashtable_remove(ds);
+			btrfsic_dev_state_free(ds);
+		}
+	}
+
+	if (NULL == state) {
+		pr_info("btrfsic: error, cannot find state information on umount!\n");
+		mutex_unlock(&btrfsic_mutex);
+		return;
+	}
+
+	/*
+	 * Don't care about keeping the lists' state up to date,
+	 * just free all memory that was allocated dynamically.
+	 * Free the blocks and the block_links.
+	 */
+	list_for_each_entry_safe(b_all, tmp_all, &state->all_blocks_list,
+				 all_blocks_node) {
+		struct btrfsic_block_link *l, *tmp;
+
+		list_for_each_entry_safe(l, tmp, &b_all->ref_to_list,
+					 node_ref_to) {
+			if (state->print_mask & BTRFSIC_PRINT_MASK_VERBOSE)
+				btrfsic_print_rem_link(state, l);
+
+			l->ref_cnt--;
+			if (0 == l->ref_cnt)
+				btrfsic_block_link_free(l);
+		}
+
+		if (b_all->is_iodone || b_all->never_written)
+			btrfsic_block_free(b_all);
+		else
+			pr_info("btrfs: attempt to free %c-block @%llu (%s/%llu/%d) on umount which is not yet iodone!\n",
+			       btrfsic_get_block_type(state, b_all),
+			       b_all->logical_bytenr, b_all->dev_state->name,
+			       b_all->dev_bytenr, b_all->mirror_num);
+	}
+
+	mutex_unlock(&btrfsic_mutex);
+
+	kvfree(state);
+}