ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
		struct ext2_xattr_header *header)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *new_bh = NULL;
	int error;
	struct mb2_cache *ext2_mb_cache = EXT2_SB(sb)->s_mb_cache;

	if (header) {
		new_bh = ext2_xattr_cache_find(inode, header);
		if (new_bh) {
			/* We found an identical block in the cache. */
			if (new_bh == old_bh) {
				ea_bdebug(new_bh, "keeping this block");
			} else {
				/* The old block is released after updating
				   the inode.  */
				ea_bdebug(new_bh, "reusing block");

				error = dquot_alloc_block(inode, 1);
				if (error) {
					unlock_buffer(new_bh);
					goto cleanup;
				}
				le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
				ea_bdebug(new_bh, "refcount now=%d",
					le32_to_cpu(HDR(new_bh)->h_refcount));
			}
			unlock_buffer(new_bh);
		} else if (old_bh && header == HDR(old_bh)) {
			/* Keep this block. No need to lock the block as we
			   don't need to change the reference count. */
			new_bh = old_bh;
			get_bh(new_bh);
			ext2_xattr_cache_insert(ext2_mb_cache, new_bh);
		} else {
			/* We need to allocate a new block */
			ext2_fsblk_t goal = ext2_group_first_block_no(sb,
						EXT2_I(inode)->i_block_group);
			int block = ext2_new_block(inode, goal, &error);
			if (error)
				goto cleanup;
			ea_idebug(inode, "creating block %d", block);

			new_bh = sb_getblk(sb, block);
			if (unlikely(!new_bh)) {
				ext2_free_blocks(inode, block, 1);
				mark_inode_dirty(inode);
				error = -ENOMEM;
				goto cleanup;
			}
			lock_buffer(new_bh);
			memcpy(new_bh->b_data, header, new_bh->b_size);
			set_buffer_uptodate(new_bh);
			unlock_buffer(new_bh);
			ext2_xattr_cache_insert(ext2_mb_cache, new_bh);
			
			ext2_xattr_update_super_block(sb);
		}
		mark_buffer_dirty(new_bh);
		if (IS_SYNC(inode)) {
			sync_dirty_buffer(new_bh);
			error = -EIO;
			if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
				goto cleanup;
		}
	}

	/* Update the inode. */
	EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
	inode->i_ctime = CURRENT_TIME_SEC;
	if (IS_SYNC(inode)) {
		error = sync_inode_metadata(inode, 1);
		/* In case sync failed due to ENOSPC the inode was actually
		 * written (only some dirty data were not) so we just proceed
		 * as if nothing happened and cleanup the unused block */
		if (error && error != -ENOSPC) {
			if (new_bh && new_bh != old_bh) {
				dquot_free_block_nodirty(inode, 1);
				mark_inode_dirty(inode);
			}
			goto cleanup;
		}
	} else
		mark_inode_dirty(inode);

	error = 0;
	if (old_bh && old_bh != new_bh) {
		/*
		 * If there was an old block and we are no longer using it,
		 * release the old block.
		 */
		lock_buffer(old_bh);
		if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
			__u32 hash = le32_to_cpu(HDR(old_bh)->h_hash);

			/*
			 * This must happen under buffer lock for
			 * ext2_xattr_set2() to reliably detect freed block
			 */
			mb2_cache_entry_delete_block(ext2_mb_cache,
						     hash, old_bh->b_blocknr);
			/* Free the old block. */
			ea_bdebug(old_bh, "freeing");
			ext2_free_blocks(inode, old_bh->b_blocknr, 1);
			mark_inode_dirty(inode);
			/* We let our caller release old_bh, so we
			 * need to duplicate the buffer before. */
			get_bh(old_bh);
			bforget(old_bh);
		} else {
			/* Decrement the refcount only. */
			le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
			dquot_free_block_nodirty(inode, 1);
			mark_inode_dirty(inode);
			mark_buffer_dirty(old_bh);
			ea_bdebug(old_bh, "refcount now=%d",
				le32_to_cpu(HDR(old_bh)->h_refcount));
		}
		unlock_buffer(old_bh);
	}

cleanup:
	brelse(new_bh);

	return error;
}