Merge branch 'integrity-check-patch-v2' of git://btrfs.giantdisaster.de/git/btrfs into integration

Conflicts:
	fs/btrfs/ctree.h
	fs/btrfs/super.c

Signed-off-by: Chris Mason <chris.mason@oracle.com>

10 files changed, 3201 insertions, 10 deletions

diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
index ecb9fd3be14..d33f01c08b6 100644
--- a/fs/btrfs/Kconfig
+++ b/fs/btrfs/Kconfig
@@ -31,3 +31,22 @@ config BTRFS_FS_POSIX_ACL
 	  Linux website <http://acl.bestbits.at/>.
 
 	  If you don't know what Access Control Lists are, say N
+
+config BTRFS_FS_CHECK_INTEGRITY
+	bool "Btrfs with integrity check tool compiled in (DANGEROUS)"
+	depends on BTRFS_FS
+	help
+	  Adds code that examines all block write requests (including
+	  writes of the super block). The goal is to verify that the
+	  state of the filesystem on disk is always consistent, i.e.,
+	  after a power-loss or kernel panic event the filesystem is
+	  in a consistent state.
+
+	  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
+	  during the run of a regression test, say N
diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 70798407b9a..0c4fa2befae 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -11,3 +11,4 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
 	   reada.o backref.o ulist.o
 
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
+btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
new file mode 100644
index 00000000000..ad0b3ba735b
--- /dev/null
+++ b/fs/btrfs/check-integrity.c
@@ -0,0 +1,3068 @@
+/*
+ * Copyright (C) STRATO AG 2011.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+/*
+ * 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 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.
+ */
+
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/buffer_head.h>
+#include <linux/mutex.h>
+#include <linux/crc32c.h>
+#include <linux/genhd.h>
+#include <linux/blkdev.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "extent_io.h"
+#include "disk-io.h"
+#include "volumes.h"
+#include "print-tree.h"
+#include "locking.h"
+#include "check-integrity.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_BLOCK_SIZE PAGE_SIZE
+
+#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
+
+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:2;	/* 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_bh_private;
+	union {
+		bio_end_io_t *bio;
+		bh_end_io_t *bh;
+	} orig_bio_bh_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 refered 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 *data;
+	struct buffer_head *bh;	/* do not use if set to NULL */
+};
+
+/* 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_root *root;
+	u64 max_superblock_generation;
+	struct btrfsic_block *latest_superblock;
+};
+
+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(
+		struct block_device *bdev,
+		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,
+				     struct btrfs_header *hdr,
+				     int limit_nesting, int force_iodone_flag);
+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 int btrfsic_map_superblock(struct btrfsic_state *state, u64 bytenr,
+				  u32 len, struct block_device *bdev,
+				  struct btrfsic_block_data_ctx *block_ctx_out);
+static void btrfsic_release_block_ctx(struct btrfsic_block_data_ctx *block_ctx);
+static int btrfsic_read_block(struct btrfsic_state *state,
+			      struct btrfsic_block_data_ctx *block_ctx);
+static void btrfsic_dump_database(struct btrfsic_state *state);
+static int btrfsic_test_for_metadata(struct btrfsic_state *state,
+				     const u8 *data, unsigned int size);
+static void btrfsic_process_written_block(struct btrfsic_dev_state *dev_state,
+					  u64 dev_bytenr, u8 *mapped_data,
+					  unsigned int len, struct bio *bio,
+					  int *bio_is_patched,
+					  struct buffer_head *bh,
+					  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, int bio_error_status);
+static void btrfsic_bh_end_io(struct buffer_head *bh, int uptodate);
+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(
+		struct block_device *bdev);
+static void btrfsic_cmp_log_and_dev_bytenr(struct btrfsic_state *state,
+					   u64 bytenr,
+					   struct btrfsic_dev_state *dev_state,
+					   u64 dev_bytenr, char *data);
+
+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_bh_private = NULL;
+	b->orig_bio_bh_end_io.bio = 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 list_head *elem;
+
+	list_for_each(elem, h->table + hashval) {
+		struct btrfsic_block *const b =
+		    list_entry(elem, struct btrfsic_block,
+			       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 list_head *elem;
+
+	list_for_each(elem, h->table + hashval) {
+		struct btrfsic_block_link *const l =
+		    list_entry(elem, struct btrfsic_block_link,
+			       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)) &
+	     (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(
+		struct block_device *bdev,
+		struct btrfsic_dev_state_hashtable *h)
+{
+	const unsigned int hashval =
+	    (((unsigned int)((uintptr_t)bdev)) &
+	     (BTRFSIC_DEV2STATE_HASHTABLE_SIZE - 1));
+	struct list_head *elem;
+
+	list_for_each(elem, h->table + hashval) {
+		struct btrfsic_dev_state *const ds =
+		    list_entry(elem, struct btrfsic_dev_state,
+			       collision_resolving_node);
+
+		if (ds->bdev == bdev)
+			return ds;
+	}
+
+	return NULL;
+}
+
+static int btrfsic_process_superblock(struct btrfsic_state *state,
+				      struct btrfs_fs_devices *fs_devices)
+{
+	int ret;
+	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 pass;
+
+	BUG_ON(NULL == state);
+	selected_super = kmalloc(sizeof(*selected_super), GFP_NOFS);
+	if (NULL == selected_super) {
+		printk(KERN_INFO "btrfsic: error, kmalloc failed!\n");
+		return -1;
+	}
+
+	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);
+		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) {
+		printk(KERN_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)
+				printk(KERN_INFO "root@%llu\n",
+				       (unsigned long long)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)
+				printk(KERN_INFO "chunk@%llu\n",
+				       (unsigned long long)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)
+				printk(KERN_INFO "log@%llu\n",
+				       (unsigned long long)next_bytenr);
+			break;
+		}
+
+		num_copies =
+		    btrfs_num_copies(&state->root->fs_info->mapping_tree,
+				     next_bytenr, PAGE_SIZE);
+		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
+			printk(KERN_INFO "num_copies(log_bytenr=%llu) = %d\n",
+			       (unsigned long long)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;
+			struct btrfs_header *hdr;
+
+			ret = btrfsic_map_block(state, next_bytenr, PAGE_SIZE,
+						&tmp_next_block_ctx,
+						mirror_num);
+			if (ret) {
+				printk(KERN_INFO "btrfsic:"
+				       " btrfsic_map_block(root @%llu,"
+				       " mirror %d) failed!\n",
+				       (unsigned long long)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)BTRFSIC_BLOCK_SIZE) {
+				printk(KERN_INFO
+				       "btrfsic: read @logical %llu failed!\n",
+				       (unsigned long long)
+				       tmp_next_block_ctx.start);
+				btrfsic_release_block_ctx(&tmp_next_block_ctx);
+				kfree(selected_super);
+				return -1;
+			}
+
+			hdr = (struct btrfs_header *)tmp_next_block_ctx.data;
+			ret = btrfsic_process_metablock(state,
+							next_block,
+							&tmp_next_block_ctx,
+							hdr,
+							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_super_block *super_tmp;
+	u64 dev_bytenr;
+	struct buffer_head *bh;
+	struct btrfsic_block *superblock_tmp;
+	int pass;
+	struct block_device *const superblock_bdev = device->bdev;
+
+	/* super block bytenr is always the unmapped device bytenr */
+	dev_bytenr = btrfs_sb_offset(superblock_mirror_num);
+	bh = __bread(superblock_bdev, dev_bytenr / 4096, 4096);
+	if (NULL == bh)
+		return -1;
+	super_tmp = (struct btrfs_super_block *)
+	    (bh->b_data + (dev_bytenr & 4095));
+
+	if (btrfs_super_bytenr(super_tmp) != dev_bytenr ||
+	    strncmp((char *)(&(super_tmp->magic)), BTRFS_MAGIC,
+		    sizeof(super_tmp->magic)) ||
+	    memcmp(device->uuid, super_tmp->dev_item.uuid, BTRFS_UUID_SIZE)) {
+		brelse(bh);
+		return 0;
+	}
+
+	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) {
+			printk(KERN_INFO "btrfsic: error, kmalloc failed!\n");
+			brelse(bh);
+			return -1;
+		}
+		/* 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)
+			printk(KERN_INFO "New initial S-block (bdev %p, %s)"
+			       " @%llu (%s/%llu/%d)\n",
+			       superblock_bdev, device->name,
+			       (unsigned long long)dev_bytenr,
+			       dev_state->name,
+			       (unsigned long long)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:
+			tmp_disk_key.objectid =
+			    cpu_to_le64(BTRFS_ROOT_TREE_OBJECTID);
+			additional_string = "initial root ";
+			next_bytenr = btrfs_super_root(super_tmp);
+			break;
+		case 1:
+			tmp_disk_key.objectid =
+			    cpu_to_le64(BTRFS_CHUNK_TREE_OBJECTID);
+			additional_string = "initial chunk ";
+			next_bytenr = btrfs_super_chunk_root(super_tmp);
+			break;
+		case 2:
+			tmp_disk_key.objectid =
+			    cpu_to_le64(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(&state->root->fs_info->mapping_tree,
+				     next_bytenr, PAGE_SIZE);
+		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
+			printk(KERN_INFO "num_copies(log_bytenr=%llu) = %d\n",
+			       (unsigned long long)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, PAGE_SIZE,
+					      &tmp_next_block_ctx,
+					      mirror_num)) {
+				printk(KERN_INFO "btrfsic: btrfsic_map_block("
+				       "bytenr @%llu, mirror %d) failed!\n",
+				       (unsigned long long)next_bytenr,
+				       mirror_num);
+				brelse(bh);
+				return -1;
+			}
+
+			next_block = btrfsic_block_lookup_or_add(
+					state, &tmp_next_block_ctx,