Btrfs: fix space leak when we fail to reserve metadata space

	 * If the inodes csum_bytes is the same as the original

	 * csum_bytes then we know we haven't raced with any free()ers

	 * so we can just reduce our inodes csum bytes and carry on.

	 * Otherwise we have to do the normal free thing to account for

	 * the case that the free side didn't free up its reserve

	 * because of this outstanding reservation.

	 */

	if (BTRFS_I(inode)->csum_bytes == csum_bytes)

	if (BTRFS_I(inode)->csum_bytes == csum_bytes) {

		calc_csum_metadata_size(inode, num_bytes, 0);

	} else {

		u64 orig_csum_bytes = BTRFS_I(inode)->csum_bytes;

		u64 bytes;

		/*

		 * This is tricky, but first we need to figure out how much we

		 * free'd from any free-ers that occured during this

		 * reservation, so we reset ->csum_bytes to the csum_bytes

		 * before we dropped our lock, and then call the free for the

		 * number of bytes that were freed while we were trying our

		 * reservation.

		 */

		bytes = csum_bytes - BTRFS_I(inode)->csum_bytes;

		BTRFS_I(inode)->csum_bytes = csum_bytes;

		to_free = calc_csum_metadata_size(inode, bytes, 0);

		/*

		 * Now we need to see how much we would have freed had we not

		 * been making this reservation and our ->csum_bytes were not

		 * artificially inflated.

		 */

		BTRFS_I(inode)->csum_bytes = csum_bytes - num_bytes;

		bytes = csum_bytes - orig_csum_bytes;

		bytes = calc_csum_metadata_size(inode, bytes, 0);

		/*

		 * Now reset ->csum_bytes to what it should be.  If bytes is

		 * more than to_free then we would have free'd more space had we

		 * not had an artificially high ->csum_bytes, so we need to free

		 * the remainder.  If bytes is the same or less then we don't

		 * need to do anything, the other free-ers did the correct

		 * thing.

		 */

		BTRFS_I(inode)->csum_bytes = orig_csum_bytes - num_bytes;

		if (bytes > to_free)

			to_free = bytes - to_free;

		else

		to_free = calc_csum_metadata_size(inode, num_bytes, 0);

			to_free = 0;

	}

	spin_unlock(&BTRFS_I(inode)->lock);

	if (dropped)

		to_free += btrfs_calc_trans_metadata_size(root, dropped);