diff --git a/src/add-ons/kernel/file_systems/xfs/BPlusTree.cpp b/src/add-ons/kernel/file_systems/xfs/BPlusTree.cpp
new file mode 100644
index 0000000000..f199e10903
--- /dev/null
+++ b/src/add-ons/kernel/file_systems/xfs/BPlusTree.cpp
@@ -0,0 +1,89 @@
+#include "BPlusTree.h"
+
+void bplustree_short_block::SwapEndian()
+{
+	bb_magic = B_BENDIAN_TO_HOST_INT32(bb_magic);
+	bb_level = B_BENDIAN_TO_HOST_INT16(bb_level);
+	bb_numrecs = B_BENDIAN_TO_HOST_INT16(bb_numrecs);
+	bb_leftsib = B_BENDIAN_TO_HOST_INT32(bb_leftsib);
+	bb_rightsib = B_BENDIAN_TO_HOST_INT32(bb_rightsib);
+}
+
+
+void bplustree_long_block::SwapEndian()
+{
+	bb_magic = B_BENDIAN_TO_HOST_INT32(bb_magic);
+	bb_level = B_BENDIAN_TO_HOST_INT16(bb_level);
+	bb_numrecs = B_BENDIAN_TO_HOST_INT16(bb_numrecs);
+	bb_leftsib = B_BENDIAN_TO_HOST_INT64(bb_leftsib);
+	bb_rightsib = B_BENDIAN_TO_HOST_INT64(bb_rightsib);
+}
+
+
+void xfs_alloc_rec::SwapEndian()
+{
+	ar_startblock = B_BENDIAN_TO_HOST_INT32(ar_startblock);
+	ar_blockcount =  B_BENDIAN_TO_HOST_INT32(ar_blockcount);
+}
+
+
+uint32 BPlusTree::BlockSize(){
+	return fVolume.SuperBlock().BlockSize();
+}
+
+
+int BPlusTree::RecordSize(){
+	if (fRecType == ALLOC_FLAG)
+		return XFS_ALLOC_REC_SIZE;
+}
+
+
+int BPlusTree::MaxRecords(bool leaf){
+	int blockLen = BlockSize();
+	
+	if (fPtrType == SHORT_BLOCK_FLAG)
+		blockLen - XFS_BTREE_SBLOCK_SIZE;
+
+	if (leaf){
+		if (fRecType == ALLOC_FLAG)
+			return blockLen/sizeof(xfs_alloc_rec_t);
+	}
+	else {
+		if (fKeyType) == ALLOC_FLAG){
+			return blockLen/(sizeof(xfs_alloc_key_t)
+							+ sizeof(xfs_alloc_ptr_t));
+		}
+	}
+}
+
+
+int BPlusTree::KeyLen(){
+	if (fKeyType == ALLOC_FLAG) return XFS_ALLOC_REC_SIZE;
+}
+
+
+int BPlusTree::BlockLen(){
+	if(fPtrType == LONG_BLOCK_FLAG) return XFS_BTREE_LBLOCK_SIZE;
+	else return XFS_BTREE_SBLOCK_SIZE;
+}
+
+
+int BPlusTree::PtrLen(){
+	if(fPtrType == LONG_BLOCK_FLAG) return sizeof(uint64);
+	else return sizeof(uint32);
+}
+
+
+int BPlusTree::RecordOffset(int pos){
+	return BlockLen() + (pos-1)*RecordSize();
+}
+
+
+int BPlusTree::KeyOffset(int pos){
+	return BlockLen() + (pos-1)*KeyLen();
+}
+
+
+int BPlusTree::PtrOffset(int pos, int level){
+	return BlockLen() + MaxRecords(level>0)*KeyLen() + (pos-1)*PtrLen();
+}
diff --git a/src/add-ons/kernel/file_systems/xfs/BPlusTree.h b/src/add-ons/kernel/file_systems/xfs/BPlusTree.h
new file mode 100644
index 0000000000..d9e0828b20
--- /dev/null
+++ b/src/add-ons/kernel/file_systems/xfs/BPlusTree.h
@@ -0,0 +1,131 @@
+#ifndef _BPLUS_TREE_H_
+#define _BPLUS_TREE_H_
+
+#include "system_dependencies.h"
+
+/* Allocation B+ Tree Format */
+#define XFS_ABTB_MAGICNUM 0x41425442	// For block offset B+Tree
+#define XFS_ABTC_MAGICNUM 0x41425443	// For block count B+ Tree
+
+
+/* Header for Short Format btree */
+#define XFS_BTREE_SBLOCK_SIZE	18
+
+/*
+* Headers are the "nodes" really and are called "blocks". The records, keys and
+* pts are calculated using helpers
+*/
+
+struct bplustree_short_block {
+			uint32				bb_magic;
+			uint16				bb_level;
+			uint16				bb_numrecs;
+			uint32				bb_leftsib;
+			uint32				bb_rightsib;
+
+			void				SwapEndian();
+
+			uint32				Magic()
+								{ return bb_magic; }
+			
+			uint16				Level()
+								{ return bb_level; }
+
+			uint16				NumRecs()
+								{ return bb_numrecs; }
+
+			xfs_alloc_ptr_t		Left()
+								{ return bb_leftsib; }
+
+			xfs_alloc_ptr_t		Right()
+								{ return bb_rightsib;}
+}
+
+
+/* Header for Long Format btree */
+#define XFS_BTREE_LBLOCK_SIZE	24
+struct bplustree_long_block {
+			uint32				bb_magic;
+			uint16				bb_level;
+			uint16				bb_numrecs;
+			uint64				bb_leftsib;
+			uint64				bb_rightsib;
+
+			void				SwapEndian();
+
+			uint32				Magic()
+								{ return bb_magic; }
+
+			uint16				Level()
+								{ return bb_level; }
+
+			uint16				NumRecs()
+								{ return bb_numrecs; }
+
+			xfs_alloc_ptr_t		Left()
+								{ return bb_leftsib; }
+
+			xfs_alloc_ptr_t		Right()
+								{ return bb_rightsib;}
+}
+
+
+/* Array of these records in the leaf node along with above headers */
+#define XFS_ALLOC_REC_SIZE	8
+typedef struct xfs_alloc_rec {
+			uint32				ar_startblock;
+			uint32				ar_blockcount;
+
+			void				SwapEndian();
+
+			uint32				StartBlock()
+								{ return ar_startblock; }
+
+			uint32				BlockCount()
+								{ return ar_blockcount; }
+
+} xfs_alloc_rec_t, xfs_alloc_key_t;
+
+// Swap Endians while returning itself
+typedef uint32 xfs_alloc_ptr_t;	//  Node pointers, AG relative block pointer
+
+#define ALLOC_FLAG 0x1
+
+#define LONG_BLOCK_FLAG 0x1
+#define SHORT_BLOCK_FLAG 0x2
+
+union btree_ptr {
+	bplustree_long_block fLongBlock;
+	bplustree_short_block fShortBlock;
+}
+
+union btree_key {
+	xfs_alloc_key_t fAlloc;
+}
+
+union btree_rec {
+	xfs_alloc_rec_t fAlloc;
+}
+
+class BPlusTree {
+	public:
+			uint32				BlockSize();
+			int					RecordSize();
+			int					MaxRecords(bool leaf);
+			int					KeyLen();
+			int					BlockLen();
+			int					PtrLen();
+			int					RecordOffset(int pos); // get the pos'th record
+			int					KeyOffset(int pos); // get the pos'th key
+			int					PtrOffset(int pos); // get the pos'th ptr
+
+	private:
+			Volume*				fVolume;
+			xfs_agnumber_t		fAgnumber;
+			btree_ptr*			fRoot;
+			int					fRecType;
+			int					fKeyType;
+			int					fPtrType;
+}
+
+#endif
diff --git a/src/add-ons/kernel/file_systems/xfs/Volume.h b/src/add-ons/kernel/file_systems/xfs/Volume.h
index 748eb10329..f008476404 100644
--- a/src/add-ons/kernel/file_systems/xfs/Volume.h
+++ b/src/add-ons/kernel/file_systems/xfs/Volume.h
@@ -61,4 +61,4 @@ protected:
 			uint32				fFlags;
 };
 
-#endif
\ No newline at end of file
+#endif
diff --git a/src/add-ons/kernel/file_systems/xfs/xfs.cpp b/src/add-ons/kernel/file_systems/xfs/xfs.cpp
index 616290c070..e397b0b93e 100644
--- a/src/add-ons/kernel/file_systems/xfs/xfs.cpp
+++ b/src/add-ons/kernel/file_systems/xfs/xfs.cpp
@@ -11,6 +11,11 @@ XfsSuperBlock::IsValid()
 {
 	if (sb_magicnum != XFS_SB_MAGIC) return false;
 
+	if (BBLOCKSIZE <= sb_blocksize){
+		ERROR("Basic block is less than 512 bytes!");
+		return false;
+	}
+	
 	return true;
 }
 
diff --git a/src/add-ons/kernel/file_systems/xfs/xfs.h b/src/add-ons/kernel/file_systems/xfs/xfs.h
index a1d6e6fabc..633611d4cc 100644
--- a/src/add-ons/kernel/file_systems/xfs/xfs.h
+++ b/src/add-ons/kernel/file_systems/xfs/xfs.h
@@ -3,6 +3,12 @@
  * All rights reserved. Distributed under the terms of the MIT License.
  */
 
+/*
+Important:
+All fields in XFS metadata structures are in big-endian byte order
+except for log items which are formatted in host order.
+*/
+
 #ifndef _XFS_SB_H_
 #define _XFS_SB_H_
 
@@ -11,7 +17,8 @@
 
 #define XFS_SB_MAGIC 0x58465342 /* Identifies XFS. "XFSB" */
 #define XFS_SB_MAXSIZE 512
-
+#define BBLOCKLOG 9		/* Log of block size should be 9 */
+#define BBLOCKSIZE 1<<BBLOCKLOG		/* The size of a basic block should be 512 */
 
 
 /*	Version 4 superblock definition	*/
@@ -126,4 +133,46 @@ Superblock quota flags - sb_qflags
 #define XFS_SB_VERSION2_PROJID32BIT 0x0008	/* 32-bit project id */
 #define XFS_SB_VERSION2_CRCBIT 0x0010		/* Metadata checksumming */
 #define XFS_SB_VERSION2_FTYPE 0x0020
-#endif
\ No newline at end of file
+
+
+/* AG Free Space Block */
+
+/* 
+index 0 for free space B+Tree indexed by block number
+index 1 for free space B+Tree indexed by extent size
+
+Version 5 has XFS_BT_NUM_AGF defined as 3. This is because the index 2 is
+for reverse-mapped B+Trees. I have spare0/1 defined here instead.
+*/
+
+#define XFS_BTNUM_AGF 2
+#define XFS_AG_MAGICNUM 0x58414746
+class AGFreeSpace{
+	public:
+			void			SwapEndian();
+	private:
+			uint32			magicnum;
+			uint32			versionnum;		// should be set to 1
+			uint32			seqno;	// defines the ag number for the sector
+			uint32			length;	// size of ag in fs blocks
+			uint32			roots[XFS_BTNUM_AGF];	// roots of trees
+			uint32			spare0;		//spare
+			uint32			levels[XFS_BTNUM_AGF];	// tree levels
+			uint32			spare1;		//spare
+			uint32			flfirst;	// index to first free list block
+			uint32			fllast;		// index to last free list block
+			uint32			flcount;	// number of blocks in freelist
+			uint32			freeblks;	// current num of free blocks in AG
+			uint32			longest;	// no.of blocks of longest
+											// contiguous free space in the AG
+
+			/*number of blocks used for the free space B+trees.
+			This is only used if the XFS_SB_VERSION2_LAZYSBCOUNTBIT
+			bit is set in sb_features2
+			*/
+
+			uint32			btreeblks;
+}
+
+
+#endif
diff --git a/src/add-ons/kernel/file_systems/xfs/xfs_types.h b/src/add-ons/kernel/file_systems/xfs/xfs_types.h
index a2940bfcfc..3b1fd6e379 100644
--- a/src/add-ons/kernel/file_systems/xfs/xfs_types.h
+++ b/src/add-ons/kernel/file_systems/xfs/xfs_types.h
@@ -38,4 +38,4 @@ typedef int64 xfs_fsize_t;		// byte size of a file
 
 // typedef unsigned char uuid_t[16];
 
-#endif
\ No newline at end of file
+#endif